It has terrible documentation, no doubt about it. However, depending on your setup requirements, the installation procedure can be quite acceptable. It should finally have a graphical installer.
If you're not doing anything complicated like programming, hosting your own services, or planning on using rare software that you yourself have to package, it can be a very low maintenance OS.
My single biggest tip: before installing something, check if it has an "option"
For example, if you want to use KDE as your desktop environment, you need the services.xserver.desktopManager.plasma5.enable option. Use the option search. It's often easier than listing the individual packages manually and writing their configuration manually.
The reason for this is that nixos doesn't have "meta" packages. Those are packages that just contain other packages. Most package only has the absolute minimum it needs to be built - not run. The KDE desktop environment requires many packages to run.
Additionally, package configuration normally happens outside of the package in a declarative manner. You don't write /etc/network.d/111_startup.sh. That's either in an option environment.etc"network.d/111_startup.sh" or (making this up) networking.startupScripts which puts a value in to environment.etc"network.d/{script.name}.
Do no be afraid to ask for help. The nix community is aware of the documentation disaster it has on its hands.
Yes, the nix foundation is slow and doesn't have its own wiki - no idea why.