Do you adjust your subwoofer

No, because I don’t use the same system/s for both music and movies (different rooms). Once I set subwoofers to my liking, I leave them alone regardless of what they are playing. If I can tell the origin of the sound coming from a sub, then it’s too loud in my opinion. For that extra "thrill", I turn up the entire system evenly, but at the end of the day everyone should do what they like right?

Mine is a set it and forget it component.  The sub's output should be proportionate to the rest of the system, and controlled by the main volume. Occasionally I'll make a minor adjustment, but the sub settings have an unofficial default setting that I've deemed ideal for the room and system.

My secondary system shares space with our modest home theater.  Both have separate subs.  The crossover and volume are quite different in both systems. The home theater crossover is higher,as welll as the volume. That is for the extra boom for movies. 

Hell yeah. Second system. No sub on main. Depends on the mood. REL S3 SHOs. Different recordings have different levels so I might make a few tweaks now and then.

The science answer would refer you to Fletcher-Munson and Harman curves. The subjectivist says turn to where it sounds right for what you're listening to. The purist epoxies the level knob in place only after excruciating critical listening sessions with curated selections. At the end of the day, you'll set it where you like the best, and don't have to mess with it too often