Earlier this year I did a speedrun of R-Type II (Arcade) and I made a vid going over my strats for the bosses, in both loops for the World version. Figured I'd post it here for posterity, maybe it will help anyone going for a 1CC. I'm not sure how well some of these work on the JP version since I think bosses have more health.
I basically go over the visual cues and some of the reasoning for the weapons I'm using.
https://www.youtube.com/watch?v=o2nxiSeH9lM