I'm not too sure about this feeling that Pex is not capable of withstanding high pressure. All of the leaks that I have had have been caused but the faulty installation of those aluminum collars(crimp rings).
It is true that those crimp fittings may loosen due to vibration in a RV but Sharkebite and other fittings are pretty reliable up to and including 120lbs pressure. Pex is used in residential plumbing and has a very high pressure rating.
Our daughters home is a vintage Mid-Century Modern with slab floors and a flat roof, there are four bathrooms and when they had it re-plumbed, the bids for copper re-piping and Pex re-piping were almost identical. The copper pipe and fittings are cheaper overall than Pex but the labor is much more intense.