NixOS has plenty of support but their leadership is controversial and squabbles in the background.
NixOS isn’t the best for security because every application runs with full permissions. Newer versions support AppArmor but not by default or for every program.
The PG recommendation is based upon resisting surveillance capitalism, not security. NixOS allows users to choose only free software or make unfree exeptions.
I like NixOS but don’t recommend it for everyone. Anything possible on normal Linux works on NixOS. The ability to install multiple versions of the same program or dependency is useful.
Reproducability is a benefit if you have multiple PCs and want the exact same software on each one. Custom keybinds and shell aliases are reproduced too, so you don’t need to worry about forgetting a dotfile.
If you understand it isn’t hardened then daily driving is fine, although there are more secure options on the market.