Would a clincher really save much weight? The rim needs to be strong enough to resist the pressure of the tire so the brake track cannot be made much thinner.
I don't know what that question means ... I don't think anyone is talking about tubular here. I think OP is just asking for recommendations on a good disc rim for road or cx. Since to-date disc rims have been for mtb, there are obviously fewer options that address the needs of road (lighter weight, maybe lower spoke counts, higher psi, etc.).
As to whether a *disc-brake* rim could be lighter than a rim-brake rim, that is another topic -- and there is industry opinion on the matter a mere google away.