+1 from me. I see everyone saying basically accurate things from different perspectives. 
Since I was asked, I’ll try to add some clarification of my own even though I think it’s mostly worked out already.
Cam Plus is not needed for GENERAL sound notifications, only for the specific AI sounds (Crying, Barking, Meowing, Talking Gunshot, Glass Breaking being labeled separately with separate notifications for only those things instead of just “ANY SOUND”).
But you are correct that Wyze should clear up the ambiguity with an improved interface to show what’s free vs premium.
They should also change the wording from saying “Other Sound” to say “ANY Sound” or “All Sound” to clarify that it includes the AI sounds too, but won’t distinguish between what type of sound it heard.
One thing that really affects sound events and notifications though, is that sound can only trigger an event once every 5 minutes and it is limited to a 12 second event. These sound limits are even in place for people paying for cam plus. However, if an event was triggered by motion, then the AI will analyze the sound during that entire motion event and not limit it to 12 seconds.
In other words, if someone is behind the camera and starts talking, but the camera doesn’t see them, it will trigger and record for 12 seconds and send an alert. However, if it had sound triggered anytime in the last 5 minutes, and now new sound is made, it will ignore that sound and not tell anyone about it until a full 5 minutes passes, then if it hears another sound, it will trigger a new 12 second event and alert. A lot of alerts get missed this way. I reported this issue to Wyze some time ago, that even cam plus subscribers are subjected to a sound cooldown, just not a motion cooldown rate limit.
In some cases this can explain why a person can stand behind the camera and yell and not get a notification, because it already detected a sound event in the last 5 minutes. samsam can better verify this by going to the events tab and using a filter to select the specific camera they are testing and then sort it to only show events with a “Sound” detected. (I think free accounts should be able to sort by sound events still). If any show up, then you can be sure sound events are actually processing. If one happened within 5 minutes of your testing of yelling at the camera, then that would explain why you didn’t get a new notification. But if it shows an event and you just didn’t get a notification for it, then there is a separate issue entirely and we need to figure out why notifications aren’t coming through (check everything @Crease posted)
Yes, if a person doesn’t have a subscription then ALL sounds get processed as “Other Sound” BUT if a person has Cam Plus, then Cam Plus will give priority to the specific subcategory of sound detected before just labeling it “Other Sound” like fmills1d is accurately explaining has been their experience while using it with the subscription.
Here is the how that is supposed to work, and they sometimes have a bug with it:
If you select “All Events” then go to custom detections, you have the option to select AI events and “Other Motion” (AKA “ALL Motion”) and “Other Sounds” (AKA “All sounds”). And in the cloud events tab, it will also show you events that didn’t have an AI detection in them.
If you select “Smart Detection Events” then in theory (not always in practice) it should disable the “Other Motion” and “Other Sound” notifications and labels and automatically delete (or hide) all cloud events that don’t have an AI detection in them. This is intended to keep your events tab clean and only show you events that have relevant AI detections in them.
Sometimes there is a glitch and selecting “Smart Detections” only hides the option to turn on or off notifications for “Other Motion” or “Other Sound” but will continue to send you notifications for those even though it is hiding the events for those from you. In that case the only way to overcome that accidental but annoying bug is to temporarily switch back from “Smart Detections” to “All Events” so the notification option will show up for you again, then go to customize and manually toggle off the notification for “Other Motion” or “Other Sound” and then you can go switch back to “Smart Events” and everything will go as intended (only get notifications for AI detections and only see AI events in the cloud events tab).
Hopefully they fixed that bug though. I haven’t seen anyone reporting it since I reported it to some employees a while ago. 
Sorry, I know that’s a little confusing.
TL;DR: I think there was just a misunderstanding and everyone was saying basically correct things from a different point of view of free vs premium, and it looks like samsam got the issue resolved.
(sorry for the late response…I have a ton going on this weekend)