I got my cabin luggage weighed by CX check-in agents once in HKG (I was GO back then) twice in SFO (That was puzzling - I was DM already and the security in SFO never bothers about that). My carry-ons were never weighed by airport securities. They seem to be more concerned about sizes.

I think the laptop is not part of the 7kg limit. I think there is a separate 4kg (or perhaps lower) limit for a laptop.