Quesy regarding Network Access vs File Access

I didn't speak about windows because, with basic concepts being the same, windows handles everything at the file level way more easily than linux does for SMB. I tend to authorize everything for everyone on the share rights on windows and locking with NTFS rights (because they give more control interestingly) while I do exactly the opposite with linux. Windows being an all in one solution for SMB/CIFS shares, that's more convenient like this (and in windows server, that's how it's meant to be since share permissions hidden in a submenu and grant everyone full control).
That said when you install other more enterprise software you use a "system account" for the software and then create users inside it like for linux (Oracle server for example works like this).

Either way the least permissive of the two applies, and an explicit deny (clicking refuse, not just letting blank on windows, depends on software for linux) will result in a denied access even if the user is a member of a group that is allowed.