I have a regular commercial PEX ring crimping tool and use both plastic and brass fittings without problems. I don't care for the mini-variety of PEX ring crimping tools.
I don't know of a "Barbed Fitting" that will hold any pressure without a clamp, can you provide a link so we will all know about them
There is a push-in fitting for PEX, but I am a little leery about using them in an RV due to vibration and shifting.
However, there is the "Flare-It" fitting line that works well and I have used for a number of repairs vs. new installs. Here's a pic. They are a little pricy, but if you only need a few it's a good way to make sure everything stays in place. They have a full range of fittings, not just those shown in this link.