I only ever used systemd for services and did not use any of the other features. Openrc does that and it works so nothing to handle.
I use seatd and I do not use polkit. The only thing that caught me off guard was that the default login binary does not support PAM so I had to install shadow-login.
I do use flatpak for lutris, web browser and few other things, but I prefer native packages. If the package isn’t in the repos I package it myself, the package format is almost identical to the one Arch has so a lot of times its enough to just edit the dependencies and build.
Yeah, its extremely minimal, but thats part of the appeal for me.
For automounting I just have udev rule for my usb drive, which is ok, but if I had to use a bunch of different drives for whatever reason I’d probably setup polkit.