I have used TCP Global for many years. Hearsay is old PPG formulas. Dunno. I have always had good luck with their topcoat and their Color Library in single stage.
I have also had good luck with local PPG store, almost always single stage. Few months ago I had 62 Ply white mixed and the mixer said "NO way this will be right." Went by the formula. "Way too muck black it will be pretty much grey" Yep I got a free gal of grey! Then used the seat of pants and next gal spot on! lol
My first time to use bc/c was bout 91 or 2? B5. DuPont. It just was not right. Close but not right.
Single stage for me. Plenty durable and it can be amazing if done right.