Like Zach said, M205 is a great 1-step. I don't really reach for it anymore because it's NOT very trim friendly.
HD Polish+ also uses SMAT abrasives and even with an aggressive foam pad generally finishes very well. It also is trim friendly, sun friendly, and smells great. It's HD Speed without the sealants/waxes/silicones which is why it's my favorite 1-step on paints with very minor marring and swirls.
Boss Correcting Cream is unbelievably good but my current bottle has practically turned into water it is so runny. The boss creams are something special and really easy to use BUT unless they are kept in a basement where the temperature is 68-72 degrees and no humidity all the boss polishes and compounds tend to get VERY runny. (Still worth it though)
If I was told I could only have one polish/compound. Scholl Concepts S20 Black would be it. It cut's great with a Rotary and wool. It finishes amazing with DA and a white polishing pad , and is the most incredible 1-step compounds I've ever used with a heavy foam polishing pad.
It's a shame Autogeek stopped carrying the Scholl Concept's line. Even if they could just offer S30+, S20 Black, and S3 Gold XXL. AG sells a ton of compounds and polishes that utilize better abrasive technology than Scholl's, but if you encounter a lot of soft/sticky paints I can't imagine trying to troubleshoot the issue without access to scholl's.
Yes! As much as 205 is a great product, I like to stay away from anything that turns trim white if I can. HD Polish+ IMO, is the “bee’s knee’s” and its the first one I usually grab for. Seems to always test out better for me, even on soft black, and that was compared to Essence. For the life of me I cant get that product to be friendly for me. HD Polish just works incredibly well and saves times.