We have taken the ferry a couple of times. The first time we were tenting and so did not get off at any of the ports. Our children were very young and getting into a port in the middle of the night and then trying to find a place to camp was the reason.
We always regretted not seeing Juneau, Ketchican etc. so in our later years we took our truck camper and did the stops. It is a great trip. The one bit of advise I have is to check the schedules very carefully and try to book your travels during daylight hours. The scenery is outstanding and it would be a shame to miss it after paying the cost of the trip (expensive). We had ferry reservations but did not worry about reserving campgrounds at any of the towns
and never had a problem. Often we would camp at the ferry dock ready to board
the next morning.