Unfortunately, I suspect I’ll end up being forced onto Wayland at some point because the easy-use distros will switch to it, and I’ll just have to get used to moving and resizing my windows manually with the mouse. Over and over. Because that’s secure.

I think you were being sarcastic but it is more secure. Less convenient though.

I’m not sure if that’s what you’re looking for but KDE has nice window rules that can affect all sorts of settings. Placement, size, appearance etc. Lot of options. And you can match them per specific windows or the whole application etc. I use it for few things, mostly to place windows on certain screens and in certain sizes.