While true, the last task is to create a general purpose machine so there’s no puzzle anymore. Only thing left to do is to make it go faster.

Now my question is, how should I deal with these pacnew files?

Install pacman-contrib which includes pacdiff. Meld is easy for beginners.

DIFFPROG="meld" pacdiff --sudo

See https://wiki.archlinux.org/title/Pacnew_files#Managing_.pac*_files for more options.

AFAIK you can skip the “download” by also copying the corresponding .acf file in the parent directory.

For documents: https://docspell.org/

For media files: https://hydrusnetwork.github.io/hydrus/index.html

Steam starts Proton inside a container and runtime. Maybe those provide some special $stuff for those games.