I guess the water thing depends a lot on where you live and what type of camping you do. Bikendan has lots of great parks in California. We have some in upstate NY, but not a lot. Promise Land Park in PA is nice too.
I always camp at full hookup sites. Part of the reasons is because of health limitation issues, so the less work the better.
We always have some water in the tank for the road and convenience, but rarely more than 1/3rd tank.
I have the 17Z and the cargo capacity has never been an issue. It's only the two of us since our son passed, and we don't have a need for a lot of "stuff" when we camp. We love out little Mighty Mite Jayco 17Z. It has everything we need and even has a sofa and a dinette which many smaller ones don't have.
I did replace the wheels and tires with 14" radials. My original tires had some cracks and the load range D 13" tires are special order and not stocked most places. The 14" are common and even have a few extra pounds capacity.
Ray