<I'm also still working on water level, because I don't want to compromise too much vertical space or soil depth. Would 2 inches be ok for ABG mix, or would I have to do 2 1/2? >

You plans look wonderful! Your Greenies are going to be very happy there.

IMO - 2 1/2 " of ABG is not deep enough. I use a 3" minimum.
Especially for the snake plant---as you want it 'in there'.
Have you though about building the soil up toward one corner?

The Pilea is going to be beautiful hanging down in the corner. It will start to grab the back ground and anchor there ----> perhaps even start to crawl.
I recently purchase 2 of the from BJ at the last White Plains show.
I have mine as ground cover in a tinc enclosure.. I divided it...and in less than 3 days it pop right back up.
It is grabbing most everything it's touching. So it will fill that corner really nicely !

Talk to Bill --- be sure you get a begonia that does not mind being stayed. The violets will be ok, but some of the begonias will be cranky.

Keep us posted