I just ordered a 707, which will be my third Carbonda build after an FM1002 (170F/150R AM 29er) and FM1003 (single crown 180mm DH/enduro 29er). Carbonda has a very solid reputation and my experiences have borne that out.
The 707 uses the same drop-in 1.5/1.5 headset setup as the FM1002, to give the option of headset cable routing. I’ve found their OEM headset to be prone to rust, knocking/creaking, and dirt/water ingress. I replaced the one on my 1002 with an FSA no.55R-558 (no cable routing) and have been very happy with it…precise tolerances so you don’t need the thin spacers the OEM headset uses to correct for imprecision, and better protected against the elements. If you want headset cable routing, the no.55 ACR should have the same benefits.
I picked the 707 for multiple reasons and didn’t even really consider VeloBuild, but looking over the CX-002’s spec sheet I see several differences in favor of the 707 if you want maximum gravel firepower…being a gravity MTB rider that’s my focus. Since you’re considering racing I’m sure your ideal is a bit different, but to my way of thinking:
*50mm clearance is better than 42
*180mm rotor clearance is better than 160
*BSA threaded BB is better than press fit
*707 strikes me, visually, as a bit more rugged
…however, you’re talking to someone who’s putting a suspension fork on his 707 that is heavier than the frame itself! I’m planning to do a substantial amount of trail riding with mine and I like to spice up my gravel rides any way I can, including small jumps that might end up not being so small with this new build.
On the flip side of that argument, thinking more like a racer: the CX-002 is significantly lighter (claimed weight)…about 300g less on the frame and 100g less on the fork.