OK so a couple of nuggets I've trial & error'd myself into understanding -
1) The wider you shoot, the less effective your astrotracer is going to be. Even with perfect calibration, extended exposure times are going to have pronounced star trails in the edges and corners still. The wider you're shooting, the worse it's going to be. It's one of those ugly things about taking the real-life vision dome that we see, and projecting it to a flat image plane.
On APS-C, I've found 14mm to be the widest where it's still kind of effective. By 16mm, the effectiveness is greatly increased.
Plus, the wider you shoot, the less you're emphasizing the more spectacular bits of the Milky Way. In fact, shooting extremely wide is sacrificing details in the juicy galactic core only to show off wider parts of the less interesting outer features... which also invites tons of uninteresting open space.
2) Light pollution filters *do* make a pronounced difference in how the sky looks. I keep an RA54 filter in front of my lens even shooting in the darkest skies. I wish I had some direct side-by-side A/B test shots to show.
3) Light painting! This is just a creative suggestion. Looking at some of the trial photos, if you're wondering why your foreground looks sort of flat, shapeless, and undefined, I'd say it's because you're shining the light directly behind the camera. While that's indeed illuminating your subject, it's also casting no shadows at all from your lens's frame of reference. That means it erases so much potential for you to add depth context and texture into your foreground elements.
Next time try walking away from your camera and shining the light directionally off-plane to where your camera is pointing. You can really craft the light to show off details in the foreground.
Example of all 3:
This is a 24mm field of view on the K-1 (probably could have shot this identically with the Samyang 16mm on my KP). 24mm equivalent is great for dialing in the interesting parts of the galactic core, while still leaving plenty of room to organize foreground elements. In North America, sometimes the Milky Way is presented perfectly vertically... for those weeks I'll shoot at 20mm instead. In the early and late parts of the season, where the Milky Way is flatter to the horizon, you can do great with a 35mm equivalent FOV too.
The RA54 filter cleaned up the blues in the sky without having to resort to an artificailly-low White Balance value, while simultaneously dialing back some of the orange at the horizon. It makes a ton of difference for color clarity in the sky.
Lastly, this is a 2-light setup to make shadow shapes with the ruins in the foreground, but the lights were also positioned to to reveal the textures in the lit brick faces. So many people shoot this spot, and use a headlamp behind the camera, and their foreground just looks like illuminated shapes of bricks, without any real context to what those bricks are.