You have been QRT for 25 years and then you go out and buy a junk radio and ask if the quality of the PL connector makes a difference.
It sounds once again, like someone that wants to come back to amateur radio that thinks that they can set the world on fire - if they buy the radio with the most technology or the biggest amplifier.

The cheap PL's with the nylon in the center are made for CB radio - a couple of watts - maybe 100 max. and are a one time use connector.

The good ones - Amphenol - are good for a couple of thousand watts and can be reused. I use crimp on connectors, not the screw on type.

The frequency range has nothing to do with the construction materials.

UHF / PL Connectors are good for maybe 500 MHz and that is it.

There are other connectors that are a lot less lossy above 500 Mhz such as the BNC.