The provided stem from VeloBuild has been problematic. It's the same exact stem from 3+ years ago which came with my VB-177 frameset. And led me to making a full video on its inherent headset play issue.
The pinch bolts aren't really the issue. You would need to run at least a 10mm spacer on this frame for bolt clearance anyway. Otherwise the lower pinch bolt is blocked by the 3D printed headset cover. It's the overall design of the stem and top cap. You basically need to cut your steer tube perfectly otherwise there will be headset play. And you can't run standard spacers above the stem. Lose lose.
I wasn't planning on using VB's stem anyway, which is why I purposely pushed for them to offer at least some compatibility with FSA/ACR. Peter's integrated cockpit from XMCS slots in perfectly into the 3D printed ACR headset cover.

Now to the topic of weight. Yeah it's heavy by comparison. I mean just look at it. A TT/track bike for the road. It's still lighter than my Specialized Allez Sprint albeit a different material. But more carbon doesn't automatically mean stiffer/harsh. In fact in my experience more carbon sometimes leads to the capability of soaking up road vibration better. Especially thick seat tubes. Less flex yes, but more vibration soak. Maybe it's all in my head.
I'm hoping this frame is ultra stiff in the BB and headtube area. Only time will tell whether or not the back end is sloppy. When it comes super aero frames in this price range, past trends usually predict future trends.