I can only confidently answer for some of these
-
the Heroic launcher is probably what you’re looking for and it should work really well. You may also be interested in looking up Lutris and Bottles for other games.
-
these should work 1:1 on most desktop enviroments from my experience. If not, they should be quite easy to configure
-
most of the time software will be available natively as a Debian package, and then other distros. Sometimes there won’t be a native package for your system, especially if you use anything outside of Debian, Arch, Fedora or their derivatives. If that happens there’s distro agnostic Flatpak, which works a charm. You also have tools like alien or dpkg, which convert formats from one system to a different one. They are slightly hit and miss, but a great tool if you’ve exhausted othe avenues
-
I vovch for what other people have said, Fedora KDE. It works out of the box, has lots of customizability and you don’t need to use the command line much at all. You might be interested in lagging one version behind (the three latest distros are supported at any given time, to allow people to skip one when updating) and install Fedora 39 so that any possible bugs are completely ironed out and compatibility of packages and programs is higher.
I would also recommend Linux Mint 21.3 (for the same reasons as I said to lag one version behind with Fedora, I would recommend to only update between one X.3 version and the next X.3 version) but the Cinnamon desktop environment might be a bit simple for what you’re looking for. It’s made for people coming from Windows though, so it will feel very familiar.
Boot them both up as a live system and fiddle around with them for a bit. You can keep your session and everything in it as long as you don’t unplug the pendrive or reboot the computer, so you can reslly take it for a week- or a month-long spin if you really want.
Have you considered running the software you need from a virtual machine inside your Linux distro?