About the teflon tape- you really aren’t supposed to use that on threaded pvc (although i do & have with no noticeable ill effects) but instead use plasto joint stik if a normal tightness when “naked” allows for leaks
www.troublefreepool.com
I remove most all my threaded connections for winter otherwise I would probably seek out the plasto stik for more permanent connections.
The deal with all the unions is so you can easily disconnect each piece of equipment for maintenance if needed without having to cut anything so keep that in mind as you are planning.
If you can’t find the appropriate magic lube for the o rings you can also use danco faucet grease (its in the faucet repair area)