Hi everyone,
I also received my LTK266-D-SL and for now everything looks really nice. The frame is very well made, no wrinkles, etc.. I went with custom paintjob, which is ok, not the best but not bad. I would say paint is relatively thin, probably the purpose behind it is keeping the weight down. My frame (size L) weighted in at 780g with derailleur hangers, forks are 330g (uncut steerer), seatpost with all hardware just under 150g...so it is indeed a lightweight frameset.
I assembled bike, but haven't ridden it yet.
Regarding the sizing - at the time I ordered the frame, only S, M, L sizes were available. At 183cm and a little less than 80cm saddle height i think it is okay, but it is a good idea to match the frameset with longer stem because it is not a very long frame in terms of reach. Also, I plan to remove spacers because I think bike will fit me okay if I slam it.
Based on what I have observed till now, it is a really nice frameset ,kudos to Long Teng

About the weight, I did not assemble my wheelset yet, but I weighed the bike with brothers' wheelset. With pedals (no bartape), it is 7.3kgs. I find this very good for a Ltwoo erx build & Magene P515 crank and Conti Grand Prix TR tires (are quite heavy). With GP5000s S TR and lighter wheelset, the bike will be ~ 7.0kg, pedals included.
Big thanks to everyone who helped make this thread very useful!