Plasitc for water ONLY under duress if the PH of the water will not allow Quality copper Tyle L above ground type K below ground
For drainage,waste and soil lines Cast Iron rules.
For vent plastic is ok as it is not scaling and is not as critical as drainage as far as noise is concerned.
Plstic on drainage means NOISE and failures.
Look at the poor VICTIMS who went for “State of the art under slab heating”
Look at the number of lawsuits with other STATE of the ART plastic failures in homes.
Now look at the Empire state building with brass piping lasting and lasting.
Look at the copper/ bronze/ muntz metals still in pristine condition after being around for several thousand years.
More important then materials is the workmanship in installation.
For your protection you want a licensed Master plumber on the job not one of his/her helpers doing the actual piping
You want proper hangers compatable with the material being used and NEVER band iron look into clevis hangers and riser clamps on the vertical.
Check the actual spacing between these hangers as not having excessive over hangs.
You should ask about not only return circulation BUT a four fitting swing to all for expansion and contraction off the hot water supply.
Ask to see the license not assume the actual man on the job is licensed and or a full mechanic.
NEVER allow an apprentice to dabble with your gas or other piping UNLESS carrying it for the real mechanic to install.
Good luck in your new home.