the mouse part is the part i like most. usually people use this kind of workflow to not use the mouse… i did the opposite. in kde with meta+left click you can move windows between monitors or to reorder them in the tiling. and with meta+right click you can resize them. this means that opening 2 windows will open them with half screen for each (because of the tiling) but with meta + mouse i can reduce one window (and thus enlarging the other), it’s very fast and very convenient.
the 20 desktops are a lot but i don’t use them all, i generally organize my work in rows. but sometimes i use the desktops differently and i like to have that kind of flexibility.
i actually used 2 activities to separate work and personal, with 2 separated Firefox profiles. so i had 40 desktops for personal and 40 for work… :)
but activities have their own set of problems, like, there is no shortcut to send a window to another activity, you have to do it from the menu in the panel. and after a reboot, sometimes windows get thrown into the wrong activity, and that’s very annoying.
to add a bit of context, i’m a software engineer, and the combination i use most is vscode on one monitor and Firefox in the other. with maybe dolphin on a neighbor desktop. this repeated 4/5 times depending on how many projects i’m working on.