I would agree, figure out the frame first and then research it and the provider/manufacturer. I purchased my first Chinese carbon frame back in October, I heavily relied on the information here and some YouTube videos. My process was:
- Identify the type of bike frame I wanted to purchase, in my case a FS XC with a 120mm of fork travel and at least a 68 degree head tube angle.
- I created a spreadsheet of all of the frames that met the criteria (or at least close enough to be considered) with the main criteria plus the metrics like seat tube angle, reach, stack, BB type, price, what's included, etc.
- Researched the top ones I was interested in by reading everything I could find here, Aliexpress ratings (although I didn't give too much weight to this) and general google searches.
- Finally pulled the trigger, I was live chatting with the provider (in my case Everjoy Industries) at the time of purchase (I was monitoring on a code release for work in the middle of the night so this was the perfect opportunity). The live chatting was moments after I made the purchase, but reassuring nonetheless. They were very responsive, sent me photos of the frame as it was prepared for shipping, threw in an extra derailleur hanger for me at my request. Overall I was pleased with them and the experience.
One of the best pieces advice I saw somewhere was to pick a frame from a brand that would put their brand name on the frame (as opposed to a knock off of some other frame without branding). I went with the Lexon Riot 10 for what it is worth, you can see my posts in that thread as I went through the research, to purchase, to build journey. Lexon brands the frame, although I went with the matte black and no Lexon branding, additionally the frame is used by a pro XC rider, Eva Lechner. If it is good enough for her, I figured it was more than good enough for me as a middle of the pack finisher in CAT 2.
Good luck and enjoy the journey.