I wouldn't buy any of the warranties, and if you've got the cash, open a separate account and put that money in, using it only for repairs on the RV. The odds are, at the end of the 4 years, you'll be way ahead.
Even the tire warranty, so many times people with extended warranties get denied. You'll be out in the wilds, with few options on where and how to get the repairs done, and the odds of the extended warranty coming through don't seem very good. They'll tell you that you have to go to a specific shop, or use a specific replacement that won't be available anywhere near where you are when you break down.
I've had two occasions to try and use an extended warranty (Ones that were given to me, I didn't buy them), and both cases were horrible examples of poor communication, poor customer service and both were denied for reasons that weren't even in the fine print. They figure most people will just give up, and they're correct.