I have no problem with the way windows work in Gnome right now. Using the window switcher is really convenient. The only things I would like to be better are 1) It's too hard to find my way back to the right window in a window group, for example if I have 4 IntelliJ-windows active and want a specific one, takes too much time to find it and they also look alike. Perhaps naming them and using some ex command (dmenu-ish) thing? 2) The window switcher is only shown on the main display. I know the Gnome devs are quite fixed in their opinions about this, but imho it would be better to show it on the active display, which I would define as where the pointer is or where I interacted last. Solve these two things and I see no need for either mosaic or tiling.
I like the app (or webpage) Workflowy. It uses bullet lists which resonates very well with my way of structuring things. I also find it better to do weekly plans than daily or context based and then just move unfinished tasks to the next week, should they not be completed. If they hang around for too long, I just delete them.