Those screw stands don’t seem to be adjustable, so mounting many boards wil most likely be a problem. Especially when many late 80s - early 90s boards had mounting holes all over the place. Otherwise, as you basically can pretty much mount baby AT mobo on ATX case, it probably works. Only thing is that only four card support brackets is little shy IMO. For your run of the mill baby AT board with no integrated peripherals, you need three cards just for the basic functionality: multi-IO, video card and sound card. If you want something like couple of sound cards and NIC, you will already have one card without support.

I have similar aluminium profile cheapo ATX test bench where you can adjust mount points much more freely and it has seven card supports. I only use it with ATX mobos, but if I’d want a vertical stand for your use case, I’d look for full size ATX one with those more customizable mounting points.