You should make a list with good/bad sellers for us .
Well from 1st hand experience alone, and this is not meant to be an exhaustive list, but I've never had problems with Far Sports, Peter (Xiamen Carbon Speed), and Long Teng. I think Chris from Velobuild is also doing a pretty good job given I suspect they track everything by hand with an excel if not a notebook (given their scale they could use an ERP). I wouldn't buy a frame from Airwolf but i'm very happy with their cockpits (allegedly T1000), which you can find on Aliexpres (on that, a friend just broke one, but he crashed at high speed because of a cat (i love that story, i dont like cats), so i dont think that means they're bad, just that well, if you crash, you can break stuff - earlier in the year he crashed in a descent and broke his front wheel).
If you can avoid it, dont buy stuff from Racework. I have mixed feelings about Winow. And definitely, definitely don't give your money to First-Class Carbon Fiber Store...