I have read a few posts over the years of some seeing CG pressure as high as 200 psi. I installed a "telltale" gauge which records max pressure and has been as high as 120 psi at some unknown CG. You just never know what a CG is going to deliver for their system pressure. If in a large CG they could turn it up high so that sites at the far end of long runs get adequate pressure. ALWAYS use a regulator - period. The last thing you want in an RV is a plumbing leak.
I don't know where some get that RVs can only handle pressure of around 45-55 psi. RVs are supposed to be capable of withstanding, and are supposed to be tested for, 100 psi or more. RVIA says max 80 psi. NFPA 1192 which covers RVs says 100 psi, or it might be 110 psi. Can't recall exactly and can't find a free version of 1192 at the moment. In Canada, plumbing systems have to comply with CSA Z240. When I spoke to RVwaterfilterstore a few years ago, he recommended running at 65 psi, so that's what our regulator is set at and after 4 seasons, zero issues.
RVs have been using PEX pipe & fittings for quite a few years now and is rated for 150 or so psi (depends on temp.) just like in houses. What I don't trust tho. is the cheap plumbing fixtures in RVs and I don't trust toilet valves in particular. Low pressure can also be a problem - our toilet started to fill once by itself on under 10 psi but happened to be their at the time...
I installed a Watts adjustable regulator and telltale gauge under the kitchen counter and ran brass pipe from there to the city water inlet. If you have a regulator at your city water inlet or inside, you should be using a high pressure rated hose. We have a Valterra one good rated a 160 psi (IIRC). I also installed a gauge behind the door to the water heater where I can easily read it.
When buying a regulator, you get what you pay for. The inline ones have a tiny orifice in them and can plug up easily with silt & debris. Sometimes they last less than one season. They should be at the faucet end of the hose to protect it but are sometimes are forgotten and left behind. Also, they have low flow rates. The good ones like a Watts 263A are rebuild-able and have a much higher flow rate. A gauge somewhere is really helpful.
If you are using a filter, some can be damaged by high pressure.