I actually think the strongest enemies are the ones that shoot projectiles, because the others (I only saw three types in total) are pretty easy to deal with. You just possess them and immediately leave, and honestly that's the best strategy I found.
For balancing, I think it could be interesting if enemies didn't die after being possessed. At first I also thought the purple parts were walls, and that you could only move along the circuits.
But overall it's still fun to literally take possession of the enemies. It definitely makes you want to see if there are new enemy types to control!