I went down the same path as you and now run NixOS. The biggest advantage is that all the tweaks you have to do every time you install are now just a couple of

I went down the same path as you and now run NixOS. The biggest advantage is that all the tweaks you have to do every time you install are now just a couple of lines in a file you only write once. It's very hard to break the system because you can always boot a previous configuration. Everything is customizable like Gentoo but if you don't modify a package its binary will be fetched from a central server so installation is very fast.