AFAIK you can use plastic pipe into compression fitting but require a pipe insert and a copper olive (not brass)
Could be wrong though so best to await one of the experts on here.
So should be all ok then
I have to be honest in saying that IMO it doesn't matter whether you use brass or copper olives as the olive seals against the fitting/nut and not the pipe. Actually, copper olives are softer and are are easier to overtighten and can actually deform the plastic and snap the insert if overdone.
If it's a new coupling, no PTFE should be needed but I find that's down to the individual.
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