Honestly, there are no weight limits or size restrictions for carry-ons. You can take whatever you want with you to the gate as long as you can get it through security… they won’t measure or weigh your bag. I have seen people with giant bags get through the security checkpoint, never questioned. Just don’t pack liquids. However, I did get through with security in ATL (not exactly a tiny airport :laugh:), forgetting to remove my liquids from my bag. No one said a thing… I didn’t realize it until later when I opened my bag and saw my ziplock baggy of liquids. :pinch:
Once you get to the gate, most airlines have curbside check-in. You can from there check your bag. You do not have to pay for the bags that you check at the gate. They do this because the overhead bins can only hold so much luggage. Your bag will come out with the rest of the checked bags.
Most smaller jets have curbside valet. This is similar, only instead of sending your bags back with the rest of the checked bags, they bring the tagged bags out with the strollers and wheelchairs that must be stored underneath. So, when you get off the plane, your bags are waiting for you. With curbside valet, you are required to check all of the larger rolling bags because there isn’t much storage on the jet.
With rolling suitcases as carry-ons, I highly recommend that you check them at the gate. It’s difficult to roll them down the aisles of the airplanes, and they are heavy and difficult to lift up into the overhead bins. Also, if you get on the airplane late, it can be difficult to find a space in the overhead bin to store your bag. So many people are bringing full-sized bags onto the plane with them because of the checked bag charges that the overhead bins are really crowded.