My experience a single rider without luggage can get on easier at the rental locations but if one just stands there queued behind entire families and their luggage, you will wait a long while. If there is someone coordinating the shuttle rides (have seen vary by agency) just let them know you are a single rider without any luggage and you will likely not wait long. The one time I was later returning, all others were at the counter being checked in and I just walked up and joined them as they finished their check-in, so for us they were checking those there without me. An important reminder when dropping off people make sure they have all their cruise documents and id so they can get into the terminal and check-in BUT make sure you as well keep with yourself your documents and id. Nothing like passing onto the significant other everything in the vehicle when dropping them off only to find out you do not even have your wallet with you when getting back to the terminal.
There is a chaotic hour (10-11 AM but seems to be moving earlier as the terminal opens earlier) when the ability of the terminal to absorb the numbers being dropped-off and trying to get into the terminal far exceeds the capacity of the porters, the two check-in points and the roads with the number of vehicles/people trying to drop-off. You will wait to get in line to drop-off/be dropped-off, you will wait in line to have your documents checks at the gates, there will be a line for security and even inside the terminal there will be line-ups to check-in. If renting and dropping-off a vehicle, I'd always avoid that hour and get there earlier or later than that one hour window.
If traffic, bio-break or other delay slow us down and we do arrive in the thick of the busiest times, one just has to relax and remember the stress of an additional 30 minutes in arriving due to the crush of all arriving for the same purpose will still have all there on-board within the same hour once boarding starts. Personally we try for as early a PAT as possible to enjoy the terminal, get any character pics taken in terminal without too long a line, get the youngest checked in to the kids clubs (get his band) without too long a line (normally none at the start) and people watch as as the terminal fills up with everyone anticipating the same cruise.