I'm getting back into flying after a long break, 5-6 years, and I dusted off my MW Extra 300, it will have a Brison 3.2.

I haven't run a gas motor since my Ohio RC Ultimate bipe about 6-7 years ago
I remember wanting to keep the Rx as far away from the engine/ignition system

For the life of me I can't remember what material is best to use for the throttle linkage.
Solid metal rod I seem to remember could translate RF to the radio?
Should I use well supported Nyrod?

tia

Nyrod will work........just remember no metal to metal contact.

had enough,

For years I've used Nyrod's with metal ends. I use a 256 rod that is threaded on one end and cut the rod to the length I need. Next I sand the unthreaded end just enough to rough it up and use CA to glue it into the end of the Nyrod. I use a Great Planes threaded coupler/Ball Link as shown in the pic and fasten the black ball to the throttle arm on the engine and screw the plastic piece that attaches to the ball onto the threaded rod. The other end I glue another 256 rod in the Nyrod and that is attached to the throttle servo.