I’m not exactly sure how it works with flatpak versions, but for native Steam+Lutris, you install it with this and Lutris picks it up automatically, as far as I remember. Probably need to allow the flatpack to see the installation directory or put it in Lutris runners altogether instead of Steam directory.
Helix is very similar to Emacs and vim/nvim, but a lot easier to set up. Tried all of them but with Helix it just clicked for me.
You can mod Minecraft pretty much into anything of your liking. Never made something as casual, but it’s possible for sure.