RVs are supposed to be tested to 100 psi at the factory by RVIA standards or NFPA 1192. Can't remember which. Doesn't matter much though, because as mentioned above, it's only as good as the connections done at the factory, and some are NOT done well. I found a leaking PEX tee behind the shower last summer. The cinch clamp hadn't been tightened properly. Not only that, they used the wrong fitting to convert from PEX to the braided vinyl hose for the toilet.
We have a Watts 263A regulator set at 65 psi. I mounted it inside under the kitchen sink. Has a good flow rate, unlike the inline ones. We have seen as high as 140 psi in a CG and have heard some reports as high as 200 psi.
A pressure gauge is good to have too. If you find that your faucets are only putting out a dribble, it's nice to be able to quickly tell if it's the CG pressure that is low.
Oh, and the better regulators can be rebuilt. The inline ones can't be and sometimes plug up due to the small orifice inside.