With Claymore, since you have Polaris cards, not only -rxboost 30, but -strap 1 or -strap 2 also. (-strap will boost way much more than -rxboost) ...think these are Windows ONLY...maybe I'm wrong
I still use Claymore for injecting straps into my RX470s while using Phoenix for actual mining.
Just start Claymore with -rxboost 30 and -strap 2, disable all cards, minimize it and then run Phoenix.
*found that while I was doing some other work with Claymore in background minimized and then I saw other people do it also with Phoenix
Sadly for me, Claymore won't work with latest drivers, so now I use it on just one rig with 18.12.1.1 driver.
With 20.8.1 Claymore just crashes for me.
It only works for Polaris cards, I think. For other cards AmdMemTweak is doing same job, but one have to know to use it...
I still haven't found right parameters for my RX470s with Hynix memory, don't have enough knowledge and time...some day, maybe, some other cards...