But is there any reason why you're looking into micromanaging service permissions?

Because I don't know any better, having very little base knowledge of linux.

The thought process here was that services like nginx should be running under a separate user from root and your main daily user account, only having access to the files it actually needs, but not really knowing how to achieve that. I know genuinely nothing about linux user management and feel a bit overwhelmed trying to figure out where to start :/ (especially comming from the all graphical UI experience of Windows)

Chmod is/was the only tool I've known about for managing permissions. I end up running stuff as root in my experimentations because I randomly run into permissions errors, but don't know how to solve them, particularly without creating more problems for other processes.

I'm using Debian as a first Linux desktop experience; previously I've done some experimenting with rpis managed via ssh, mostly to run pihole, that's about it. The rest has been windows where I was familiar.