I think that’s probably a matter of personal preference, depending upon your goals for the project, and I don’t have enough experience with this feature to give good guidance (here I’m thinking about how you might calculate storage needs vs. capture interval), but fellow Forum member @ssummerlin recently did a 5-day time lapse with q̄ 20′ captures and reported a download of only 54 MB. If I’m thinking about this correctly, then that might be a good starting point for some math:
((3 caps / hr) × (24 hrs / day)) / (54 MB / 5 days) = 6⅔ captures / MB
I also just did a 10-minute time lapse with the Interval set at 6 Sec, and that shows up as a 15.2 MB download, so…
((10 caps / min) × 10 min) / 15.2 MB ≈ 6.58 captures / MB
If you’re doing q̄ ½ hour captures, that’s…
(48 caps / day) × (1 MB / ~6.6 caps) ≈ 7.27 MB / day
You can cut that last figure in half if you’re capturing only once per hour.
Nope. At least I don’t see that kind of flexibility within the Wyze app. The Timelapse feature for Cam v4 lets me set Start (date & time), End (date & time), and Interval (03-59 Sec, 01-59 Min, or 01-59 h).
I would’ve recommended as large as possible (Cam v4 officially supports microSD cards up to 512 GB), but based on the math (if it’s correct; probably best to do your own tests and calculations) you should be able to get away with something significantly smaller (and less expensive), especially if you’re going to follow @carverofchoice’s good advice with shorter-and-more-frequent time lapse periods and especially if you’re going to be swapping cards between those periods.
For simplicity’s sake, I’ve been using 256 GB microSD cards in all of my Wyze cameras, but I’m also doing continuous recording on all those. Now that I’ve played with the time lapse feature a little, I’m curious about pulling a card (especially since you mentioned swapping them out) to see where/how these recordings are stored, because I imagine it’s different than the serial 1-minute video files I get with continuous recording. 
Another thought: If the time lapse recordings are stored as regular video files in a standard format on the microSD card, then it should be possible to just pull those off the card and manipulate those to strip out the overnight hours and end up with a daytime-only time lapse as the final product of your project, which seems like your goal here.
I’m eager to see how this turns out and hope that you’ll post to Captured on Wyze if you end up doing this.