If all devices are on the same network you should be able to control them from your 5G connection or do you mean you only want to connect to the 2.4G when the 5G is out of range.
3T doesn't do this. Not sure why they got rid of the feature. Can use Nova Launcher and get the Teslaunread add on. It's the one thing that annoys me about the phone.
I have also installed FX and I can access it from inside Play Music without headphones plugged in. I cannot access the FX settings from the sounds setting in Android with or without headphones connected. It gives me the stock android eq there.
So they removed the option to tweak the eq from inside Play Music but not if you have an alternative eq app installed. I'm struggling why they would do that.