Yeah this isn’t really much of an issue with EFI now. You can change boot order in the BIOS and things are way less likely to get overwritten or broken. You can even have 2 EFI partitions if it’s something your concerned about.
I like EndeavourOS (Arch based) and OpenSUSE Tumbleweed (or Gecko Linux). But if you prefer sticking with apt based distro Debian Sid is a rolling release.
Kind of… The problem with full DEs like GNOME and KDE is that they pull in a lot of dependencies and make a lot of changes. So it can break visuals or change icons in each others environments or install apps with duplicate functions. Something like i3 has a lot less clutter because it expects the user to build their own environment.
The best way to try out KDE would be to install it under a new user on your system so it doesn’t conflict with your original home directory. Or you could boot up a live image of Kubuntu or some other KDE flavored Linux distro and mess around with it a bit to see if you want to commit to it.
While you can install KDE on mint without issues (apt install kde-plasma-desktop) I would recommend installing a KDE focused distro because sometimes they have better default configs.
But Plasma should be able to do win + arrow keys out of the box and current versions of Plasma should have basic tiling functions by dragging a window around and holding shift. If there’s anything you don’t like it’s a very configurable platform.
It’s been working for a while unless I’m misunderstanding what you mean by screen capture. But I’ve been using OBS on KDE Wayland capturing via portals for months now with issues.
I have a framework and love it but it’s probably not the best option for this. It’s kinda overkill and they can get a bit hot and loud. More of a desk laptop than a lap laptop IMHO. Also depends on how long you need the battery to last but this is reportedly better in the newer models.