The weight limits for carry-on bags are generally the same regardless of class, they're based on safety for the overhead bins (falling onto people's heads etc).
Even with that rationale, there is no consistency: 10kg is common, 7kg is known (thank you Qantas), and Aerolineas (don't care if I spelt that right) say
4kg. Then the airline web sites say one thing about size measurements, the "cabin bag size check" frames at the gates don't match the published rules, and it's all a matter of luck what happens on a particular day.
I used a standard wheeled carry on for flying (not a camera bag). All I did was wheel it carefully (it liked to overbalance, ahem!) and wheel it right up to the counter at check in so that it was not visible to the check in staff. (Security you know -- must keep your luggage under your control at all times, right? )
For insurance I had a photographer's vest in the bag and I had plenty of pockets, but the bag was 24kg and was not weighed once. Fortunately our only Qantas flight was domestic from Sydney to Melbourne (Qantas have a reputation for weighing bags, at least out of Melbourne), and to my astonishment the Qantas flight staff were polite.
As a mild anti-theft and tampering precaution I put a zip tie on my checked luggage. It also helps stop the zip coming open as the baggage handlers through the bags around. (If you do this, don't put the zip ties in the checked bag and do have a knife or scissors in an outside pocket of the bag if you hope to open it before getting to your hotel!)
Giles