This is interesting and subjective. A shared workspace is completely unacceptable to me. I need my monitors to have different, unlinked workspaces that can be independently switched. It's one of the things I hated about using Gnome.

can you expand on that? how does it compare to sway, for example? what's unacceptable and acceptable for you?

Sway (and most other tiling) WMs have the same behaviour; i.e., each monitor has its own unique set of workspaces instead of one workspace being shared across monitors. Workspaces not being persistent also messed with me, I have eight workspaces all divvied up for exact purposes and sometimes the ones inbetween are empty.

I use labwc currently which has the ideal workspace behaviour (one workspace shared).

right, those are the two ways.

and how does niri do it? a workspace is shared among all monitor, or it's one workspace per monitor?