would these be ok for cx / gravel use – anyone tried?

Yes, have some laced to Bor rims. Although if you wanted quicker pick up go for the classic hubs

Yes. My mates had a set for years on his cross bike with no problems

Relaible hubs and light too but overpriced when you consider the tools needed to take them apart for a full service ( which they will need at some point).

Royce hubs are equally relaible have a ti freehub unike the Chris kings (the r45 campagnolo freehub has very slender splines leset of too slender for my eyes) and only 100g or so heavier. They come apart without toolsas well. For the cheap reliable set of rim brake hubs try miche primato or miche Syntium for disc brake. White industries make very reliable hubs that are simple to maintain for rim brake and disc brake.

DT Swiss 240 disc brake hubs are the best in my opinion and don’t cost as much as Chris kings.

I found Royce went through bearings very quickly. My mate (the same guy with the R45s) cracked the rear hubshell twice