Unfortunately, nothing is standard. So I would say, across all the configs you looked at, which had a file and module structure that you understood? I'd follow that then.
My config has a users and hosts dir, to distinguish home manager and nixos configs. Inside each is the list of users and hosts configuration files. In addition, there is a modules folder that holds modules that are common among different users/hosts.
Niri looks really cool. I've used tiling WM before but scrolling is a unique take, perhaps more productive for some folks?
Nushell is a good one. I do data science for a living and it'd be nice to have the shell handle some small data transformations instead of writing a script in python. But all the syntax and behavior is very different than bash, so I've been afraid to start because of the learning curve.