As someone who has not experienced any high-performance frameset, I would also love to hear about the differences between the 268 and the SL8. No one expects the VB to be better than the SL8, but as pearl said, how close can the VB get if you invest the price difference in better components like the wheels or the groupset

Two months have passed since VB agreed to send me a new seat clamp, and I'm still waiting. They said there was a problem with the shipment... I think the best option now is to try to get an SL7 seat clamp, as it appears VB used the same design.

After 2000 km, the only issue I found is the headset becoming loose, I had to adjust the preload a couple of times. Otherwise, it's a fine frame.

Update on my 268

Highs
-I love the Mavic thru-axle system. It's quite convenient actually. Being able to keep the axles in place when both transporting the bike and working on it on a mechanic stand is great.

-The bike is both stiff and nimble enough. I can't say there really is any discernible difference in stiffness compared to other bikes. Unless you are truly sprinting or climbing, there will be plenty of other variables in regards to maintaining any set speed.

-Visually I appreciate the frame design. Obviously because it looks like an SL7/Venge. Well rounded proportions. The sloping top tube gives the visual impression of an extreme saddle-to-handlebar drop versus a more horizontal top tube. More exposed seatpost (should?) also means more comfort as the seatpost has the ability to flex. 32c GP5000 tubeless fits no problem.

Lows
-Zero setback seatpost. It's not fully problematic for me, but I had to move my saddle back far more than I'm accustomed to. If this was my only road bike it would most likely be a deal breaker. A non-issue for most folks however.

-7x9 saddle clamp for carbon rails. On my particular clamp when using my AliExpress carbon saddle (7x9 rails), visually it does not appear as if the clamps are fully engaging with the rails. Other 268 owners with carbon saddles have not experienced this, and so far the saddle has stayed put. However, the saddle clamp bolt is now slightly bent from trying secure to the rails. Also a non-issue if you're using 7x7 rails as VB also supplies clamps for that too. Just something to be aware of.

-While the bike as a whole rides better than my previous VeloBuild frames, it does still suffer some from road chatter at the rear triangle. Rough pavement can upset the back end. Thankfully though still far better than my Dengfu R12 and TanTan x38 in this regard. This is completely subjective and anecdotal of course. Over the past few weeks I've made an effort to rotate riding each of my bikes everyday day to get a good feel on the differences and overall riding dynamics.

Closing
It's a great DIY bike at the price point so far. As always, wheel selection and bike fit/position will do most of the heavy lifting. If I could change anything it would be adding more reach to cockpit to offset the zero setback seatpost. Dear VeloBuild: Please make one for me thanks!

I also encountered the issue with the 7x9 saddle clamp. I reached out to Velobuild and they sent me a new one. I have not received it yet but I'll comment once I have it.