Why does my cursor change in size over certain windows? (solved in comments)

It's not really complicated. It's called "pushing not ready software to production".

ah thanks for sharing this :)

Relevant part:

Huge cursors in GTK4 apps

This problem is already fixed in the main branch of GTK 4, but it's not backported to 4.16 yet, probably because the fix uses a Wayland feature that Mutter doesn't support yet. So at the moment, your only option is to use a different cursor theme whose "nominal size" and "image size" are equal.

I might be missing something, but the problems seem to only be scaling issues. Why would I have the same issue on a system with 1x scaling?

Edit: nvm, apparently my system has 1,25x scaling by default