As a Home-Manager user I would argue it's not really worth it. It has it's moments for some applications but most of the time it's the same experience as editing the config files directly. Except instead of INI or TOML it's stringly typed Nix attrsets and you need to rebuild the entire system instead of restarting the app. Not exactly a huge improvement.
And that's when you're lucky enough that what you're configuring can be mapped to attrsets. Styling Waybar via Home-Manager means writing CSS but it's a multi line string in Nix with no appropriate editor support whatsoever, and writing custom actions for Nixvim means writing Neovim-Lua but... that's right, in a multi line string.
On a more positive note, I will second the recommendation for the NixOS & Flakes Book, I found it to be much more useful for getting my head around flakes (and Nix in general since I started using them fairly early on in my Nix journey) than e.g. Vimjoyer's videos, which are good but their repositories were really really cryptic to me at the beginning.
Also coming from Arch will induce a bit of a culture shock regarding documentation as the NixOS wiki is just... not very good. It's neither complete nor reliably accurate for the current release. And some wiki pages are actually just snippets with no explanation for either what they do or why they do it.