There is no perfect RV!
Only compromises.
A truck camper might be too small for 3 unless u get a giant one that requires a dually, but is perfect for towing a trailer.
If you like your boat along, then really IMO the motorhome is what you need. Get the smallest one you can stand to live in. Considering 2-3 weeks at a time you can maybe manage tight quarters as opposed to people who go months on end in one. A short one will have less coach behind the rear axle and make towing a little easier (backing up and sharp turns at least).
Driving around sight seeing in a shorty motorhome (Im imagining a short class-c) is not a big deal. You can get to a lot of places, though a little slower and with a bit more gas used.
IF you want your boat along, then get a motorhome. I would not want to deal with an inflatable where half the time it is not worth bothering with, but thats me...
