Flakes would be cool if they were easier to use/understand. Not sure if the situation has changed but when I tried to use flakes around 2-3 years ago I had a significant uphill battle in finding good documentation that I could parse, so much so that I gave up. Even getting this config to work I had to scour through their default docs, several hundreds of fellow nix user's repos, several different blog posts, and numerous youtube vids. (some apps still don't work, maybe because of Electron? hard to tell)
My previous background was manual Archlinux installs and I felt like I hit a brick wall with NixOS back then, maybe it's better? I'm still adverse but willing to try if someone could point me in a good direction to understand flakes.
Maybe split it into multiples files? Since your config is one file and 600 lines long
This I can definitely tackle👍
Check out home-manager. Very good for configuring your home directory
I know about Home Manger but I decided not to use it as I remember some incompatibilities with how I initially planned things out, I might have more information on this once I check my documentation.
imo flakes are as hard to get into as the 'normal way' if youre starting from scratch. Switching over is easier, you'll need to change quite a bit, but its a lot of boilerplate mostly. All in all I agree with the first comment tho, its worth it.
Other than that, looks good if its all working for you!