Also question is, what is your internet speed? as that might be a bottleneck there. The streaming services might just be lowering the resolution due to a bad internet connection.
Also might be worth trying chrome as the browser.
You can search up nextcloud flake and it will have all of the needed stuff, plus in the nixos search if you go to NixOS options you can see what config options it has
People yell at you if you use an excel spreadsheet as a database