You are correct on Glacier Bay...3 cruise lines have most, but not all, access to Glacier Bay. Glacier Bay is commonly described as a very desirable destination. Your hours of research HAVE given you some foundation to work on.
Time in ports is a key point. No, one cruise doesn't get the best docks. It varies by port, cruise line and time in port.
If this is your first cruise, finding a travel agent that can work with you to find your "best" is a good idea. Conversely, as you haven't cruised, I would be thinking you will be at least pretty satisfied with most any introduction to cruising. We don't know your demographic, budget, or anything else about you that goes into determining your "best".