A:AnswerIf you're referencing the USB drive see page 101.
https://usa.yamaha.com/files/download/other_assets/1/1161601/web_AV17-0087_RX-V385_om_UCABGLFP_En_A0.pdf
A:AnswerGo into settings and activate the a/v system.
Here is a link to the owners manual in pdf form. You can also download the “Yamaha AV app” it supports all Yamaha models(some actually allow the app to program it over your network.
https://usa.yamaha.com/files/download/other_assets/1/1161601/web_AV17-0087_RX-V385_om_UCABGLFP_En_A0.pdf
A:AnswerUpdate...it does send (transmit) to wireless headphones and speakers. Not sure if it can do more then one simultaneously but in the manual it use the the word "devices" as in plural.
A:AnswerI haven't done it but you can manually adj speaker volume levels, see user manual PG 70. No balance knob, use setup menu, speaker. +/- .5 db ea spkr.