I'd argue keep the copper in place as much as possible. PEX is plastic. I'm sure it contributes to all the microplastics/PFAS we see all over the place.
it's disturbing that people saying things like 'I would bet that running a single load of synthetic clothes in the dryer creates more microplastic than making 1000 cut and crimped connections of PEX tubing.' get flagged to death as if they were spamming penis enlargement pills; that comment was obviously correct