I am sure it has been answered but
PrePreg = resin already applied to the carbon, typically hardens (forms final shape) with heat (in an oven).
Wet Lay = Dry carbon where the resin is poured, dabbed, dipped or painted onto the cloth
3X = number of plys/layers, in this case 3 (duh!!!)
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The advantage of pre preg is your layers stay lined up better, for a nicer finish, and the resin ratio stays stable (ex. 30% resin to fiber) This is the preferred way to build high quality structures and it is WORLDS cleaner than wet lay. And more controllable from a quality control standpoint
The advantage of Wet lay is you have a lot more resin which typically fills pin holes and such and leads to a part that can (sometimes) be faster to prep for paint. It is also much cheaper to buy and have on hand but resin can get everywhere, I never like doing it.
Fiberglass is sometime substituted as a top layer (or bottom) because it is saves money, clear, sands better, help the mold release... It all depends on the part, manufacturer, and price point
As for our carbon ducati parts, 99.9% are cosmetic jewelry so as long as you like the look and don't yellow over time you are good to go. I question if any of it is "real high qualty" (and it does not need to be). If I hold it to the sun I can see daylight trying to shine through my factory monster carbon fender. (off of a 2005 S4R). Yea, it is thin but seems to work just fine.