Yes, the bigger you get, the more restrictions you'll find, but it's not going to be an issue 99.9% of the time.
We recently bought a 43' motorhome and had some concerns about the length limiting us. So far we've found for every place we won't fit into theres a couple we will. As example, I just finished making reservations for two months in Florida next winter, moving around between mostly state parks. I was pleasantly surprised to find we'd have no problem in far more parks than we'll ever have time to visit. One caveat, however. I do take the precaution of calling the park before making my reservation. Typically, when calling a state park, I'll get a volunteer who is very familiar with the RV lifestyle and can appreciate my concerns and limitations. At most I got recommendations of specific sites, recommended for both accessibility and beauty.
I've also found blogs of other RV folks driving/towing large rigs, some of which will frequent 'boondocking' sites, in places I would never have expected to find them. They're a great resource too. Then, of course, there's the zillion and one private parks that would be happy to take your money.
Bottom line. Buy something you want and like. With minimal research, you'll have no problem finding a place to park it.