Manuf Home Waterline Connections

[dmarino55]

Looking to replace fixtures on 1989 manuf home in bathroom, including tub. I have poly lines and original poly joints etc. New fixutures have brass connectors.

Store indicated everyone is going to these new compression joints that work on poly, copper, pex etc. at same time so I could use a compression joint versus pex.

I have hard time believing these work, do they really hold long term?

How would I get a brass water connector then to match up with the brass connector in the fixture? All i see are plastic connectors with the compression line...