How do you deal with if you need all windows appear on a single screen at the same time?
For 4 windows in one workspace, you can create two columns, each split in half. Something like this:

If you want more windows, you can shrink a column to 25%, then add a new column at 25% as well. Like this:

Does Niri support two windows tiled bottom half and top half?
Yup! That’s just a single column divided in two:



Well, autotilers are better for automatically fitting things on screen. If you want multiple windows to fit in screen in Niri, you’ll need to intervene for that (it’s pretty simple and easy, but it’s not automatic).
This is the only thing that keeps going through my mind as being objectively worse. Some small things are different, not necessarily worse or better. I think the column logic in Niri is super easy to understand, which is great, but it kinda limits tiling possibilities (not a big deal tbh, you just learn new ways to tile).