From what I've gathered while doing tons of reading through all these topics before pulling a trigger is that, if you're focused on velobuild, 268 would be your best bet. 168 was pretty good, but somwhat not stiff enough, 177 was stiffer but more lightweigt then aero focused, and 268 is mix that should be their best offer. I might be wrong, but I pulled the trigger on 268, and it's on the way in a week I hope, for my first road bike build.
LC017D from light carbon is on a good reputation from what I've seen. Seems nicely made, but the looks aren't something I fancy. That downtube...
SC-R55D looks good, weight seems really nice.
Hygge EPS moulded version also seems ok. And their stock paint job looks awesome imo. However, not sure about the retailer.
I suggest reading topics on these frames and making your decision based on what seems the best safe buy for your application. Take account on the numbers of people purchased the frame, problems encountered during assembly and after riding it... Good luck!
Considering the UCI approved frame... I had the same question, and asked a organizer for a "UCI-rule-based event", if my bike (non UCI-stickered) can enter the race, the organizer said practically: "as long it's a road bike, you can race...". So, unless he's going pro, and racing ELITE, I would bet he's fine on a frame that doesn't have the magic sticker.
