We've owned a Hybrid TT and a Class C Motorhome. High winds effected the Motorhome more than the TT, granted the Motorhome was 13' longer. I've never seen or heard of an RV that has been blown over by wind. I don't think most folks venture out in their RVs when the wind is blowing strong.
I have seen the results of Motorhomes, TTs, 5th wheels and TCs after an accident. In the accidents I have seen, it seems the Motorhomes and TCs survived the accidents the best. TTs and 5th wheels seem to implode when they flip over.
If you plan to tow a 5th wheel and the boat, you might be able to get a front mounted hitch and put the boat in the water from the front hitch. Not sure if backing up a steep boat ramp with a 5th wheel behind you will be anymore fun than having to pull forward with the TC on the truck. You could always just drop the 5th wheel before putting the boat in the water.
-Michael