I wouldn’t want to route home via the cottage and I hope that cottage via home would be acceptable.
Can I for example route the Plex sever to the cottage TV when I am there and have it locally stream to my home TV when I am home?
Lots to digest, luckily I have until April to decide what I’m going to do. I might even leave it as is. Everything is working fine except Plex quality, which I can live with it as it is not that terrible on 44" TV 
If you want the single subnet design (L2 VPN), the easiest would be to route cottage via home for everything including internet. You would not need to route the home via the cottage internet, it would only use the VPN for devices that sit at the cottage and the local internet for everything else. Basically you pick one site to be the “master” and in your case the home makes the most sense.
As I mentioned it is possible to have this setup where both use their own local internet but still can access the LAN devices over the VPN, just a bit more complex to set up, and technically a bit of a hack.
Absolutely, would essentially work just like you’re using it today just perform better/be more convenient, and be invisible to the ISPs. The question is does the plex server require mDNS, being on the same subnet, etc? I am assuming not since you’re accessing it over the internet today without issue. So unless one of those things would somehow make it work better, then standard VPN with dual subnets would allow that to work fine, just like if both were on two different networks in the same house (regular and guest is one example but not the best one).
Nah the bug has bitten you, you know you want site to site VPN now 
I can’t promise it will make any difference in the streaming quality, that could be based on latency or varying throughput on the cellular internet. But I have to imagine a direct “virtual” link would help, especially if you’re running it through a 3rd party VPN like Nord today, the site to site should be significantly lower latency and less bottlenecks in the path.
The site to site setup is primarily about security, convenience, and often a bit of performance gain. No more punching holes in your router and having to do multiple NATs in the path, etc. Things are just accessible as if they’re in the same location. Whether or not that is something you want/need, guess it depends how much stuff you do between the sites.
I have no idea as I don’t even know what mDNS is without Googling 
I know that Plex uses port 3400 for remote viewing and is not hindered by NordVPN that runs on that machine.
Not much I guess, when at home the only use of the cottage network is to access Wyze cameras. When at the cottage I view cameras at home, steam Plex and occasionally grab a file or two from my file server using either TeamViewer, AnyDesk or Screen Sharing.
But as you said, the bug has bitten me and I am probably going to pursue the task just for curiosity if nothing else. Or abandon it altogether and get something else to putts around
Mostly used by apple and IOT devices to “discover” each other and keep track of their “friendly” names. Basically a DNS server that sits on each device and they all keep each other up to date. It can result in a lot of chatter on the network if you have too many devices. It is actually a reason some end up having to create multiple subnets in their house, to reduce that broadcast and multicast traffic.
If the plex server is working over the internet it doesn’t need it, mDNS only works on LAN with no router in the path. But knowing you have apple stuff, wasn’t sure if it would be important or not. Probably would only be needed if you had apple IOT devices at the cottage that you want managed by a hub at the house or something like that.
The Wyze cams likely won’t benefit if you do the dual subnet setup, they’ll still route via the internet (I haven’t tested it but that’s typically with IOT devices, if they aren’t in the same IP range they won’t even attempt to talk to each other, sometimes they even have to share a wireless SSID). But probably not a big deal, mine all stream through Wyze due to being on a firewalled network and have always performed fine. With the single subnet / Layer 2 VPN they should be able to stream directly between the locations.
The only apple stuff I have are my computers, phones, iPads and Apple TV.
Here where things get dicey. Both locations have same SSID and password for easy setting of IoT devices, also both places have same subnet range, 192.168.4.X. How would the DHCP severs on both routers know what IPs to assign? Wouldn’t things get complicated if I keep single subnet? Maybe dual subnet would be better/simpler?
techs.
That’s it?
SSID and PW don’t matter, can stay the same. If you use the same subnet and set up the Layer 2 VPN, then one option is to disable DHCP at the cottage and let your home DHCP server assign IPs to both locations (it would also act as your default gateway and DNS server for both locations, with all cottage traffic routing via the house’s internet). That’s the easiest method, and some prefer this “single exit point” design. Main limitation here is that if home internet goes down or something causes the VPN to fail, the cottage is also down. There’s a few possible ways to have a “failback to local” at the cottage, some manual, some fairly automated, but none terribly clean.
The alternative single subnet design is more complex but it no longer relies on the VPN being up for internet to work. You set up both routers with the same subnet and subnet mask, but each one assigns a different range of IPs (different DHCP “scope”) from that subnet, and a potentially different default gateway if you want to keep all internet traffic local. So home would have 50-100 and cottage 101-150 or whatever. Then you block DHCP/BOOTP protocols over the VPN tunnel so they don’t interfere with each other.
Long story short, yes the dual subnet design is easier and less confusing to deal with. Only limitation is that stuff that relies on single subnet won’t take advantage of the VPN tunnel, but I think we’ve narrowed that down to mostly streaming the Wyze cams, and that doesn’t really matter whether it goes via their servers or not.
If it helps, for home use I find the single subnet design messy and with little to no actual benefit, and plenty of possible disadvantages. Since we’ve mostly ruled out any benefit/need in your case (unless you really really want those cams to stream “direct”), it probably doesn’t make sense to go to the extra trouble and hassle. The only time I really use it is professionally where there is a very specific need (something that has to be in the same subnet/broadcast domain or cannot traverse a router).
Or if you’re really adventurous, we can set you up with the dual subnets but use NATs to fool the Wyze servers and app into thinking all the cameras are local, that would make things good and confusing and probably throw a but of sporadic inexplicable issues in the mix too. Seems to be how some engineers I work with like to do things…
Shh the grown ups are talking 
.
I think your tech’s and @habib’s semi-amphibious ones need to get in touch and work this out. The cat can supervise with a disapproving look on its face, as is customary.
In case you haven’t figured this out, this is me and @dave27 chatting via DM, but we left the front door open so neighbours can eavesdrop
Surprised? 
Nah, I am a huge believer in KISS principle.
I am leaning towards this solution 
I live my life by it.
It is a good/common solution and would let you stream cam and stuff directly, BUT two caveats I can think of
-Whatever router/box/appliance/etc you get (and the protocol) needs to support a Layer2 VPN. L2TP is a common protocol and I see references to people running it within a wireguard tunnel. But need to ensure the device and VPN client support it.
-Within that device would need some provision to fail to the local internet at the cottage should the VPN tunnel go down (due to home internet going down or some other issue in the path). On my Asus router this is easy to do, but I haven’t done it on any other “home based” router brands. I would think most should support it one way or another, but can’t say for sure. Often stuff that seems no brainer and standard with enterprise stuff does not translate that way to home stuff, but it seems like a pretty basic function that could be done with the VPN config or even just regular static routes.
How’s your cottage in the Palisades doing with the fire? 
I feel sorry for all the So. Cal folks including all the WYZE forum members who live in that area. I think there are still 4 different fires growing in that area. I live 350 miles North of that area and we’ve had our turn in the barrel over the years. This was the sky in the afternoon in 2020. The smoke was horrible for weeks
That is horrible.
Glad your farm is safe.
I have my eyes set on this VPN router as it supports both OpenVPN and WireGuard as well as Tailscale, as I am considering to give Tailscale a try. Their free tier allows only three devices, however they count subnet routers as one device and don’t care how many devices are behind it. I will install Tailscale on my Plex server as it is already on 24/7 and take the router to the cottage. The router acts automatically as subnet router so does my Plex server. Also, it turns out that Apple TV can be used as both exit point and subnet router. If that doesn’t give me what I want, I’ll get another router and try it that way.
Looks like a capable box, probably take a bit of trial and error to get things the way you want them. I would guess the plex box may have more horsepower than the apple TV as far as getting full throughput, but who knows (not really sure what specs are on either one).
I hear reports that the fire is so bad because they ran out of water?! Fire hydrants are dry? Sad.
Just heard in the news that Doug Ford, Premier of Ontario, Canada ordered all water bombers to deploy to fire devastated areas. Quebec follows suit.
66°F and sunny, quite pleasant for South Florida. I guess the dry air is a problem?
The main problem is the wind blowing out to the Pacific, from the CA, Nevada and Utah deserts.
