The law varies by state.
Here's a link to a Good Sam's Club listing.
I don't think we've heard of anyone running into trouble for being too long at 60-62 feet combined, so either not a lot of people are over the limits, or the laws are not being enforced. Washington D.C. has a 55' limit, but having driven there for many years, I think you'd be making a serious mistake towing a 60+ footer through D.C. And according to Good Sam's list, at 50', everyone must be breaking the law in New Jersey.
As for CDL class A license, some states do require a class A non-commercial license for certain weight classes, including RVs. But as we've discussed repeatedly for at least the past 6 year, there isn't any enforcement. A Commercial Class A is not much different in terms of testing and fees, but in some states you may need an annual medical certification to hold a CDL. Some states will waive the medical if you attest that you're not driving commercially. Others won't.