I have DT 240 hubs with HED Belgium’s, I also have a spare back wheel same rim but a DT 350 hub. Can’t really tell the difference. I have about 27,000 miles on the front 240, bearings are just starting to feel a bit rough. Back 240 has maybe 20,000 miles and the 350 maybe 7,000, bearings feel perfect.
I also have November RCG 36 with 350 hubs for the gravel bike. Like them a lot. The rims see carbon 21.5mm internal I believe. Running 30mm Schwalbe Pro Ones, they measure almost 32 inflated. I can’t visualize a bike rack that would be a problem for carbon rims.