M Scaler settings question

I have two questions about M Scaler settings:

1. INPUT - Better to select WHITE/USB or AUTO-SOURCE/RED? 
2.  OP/SR - When I change color/setting from WHITE (which seems to be default setting regardless what I am listening to).   When I change color/setting I get no sound.  Only on WHITE/HIGH do I get any sound.  Having once owned a Qutest I thought the OP/SR settings where similar to filter settings on Qutest.   Any ideas why I’m “stuck” on WHITE/HIGH?

Here is my setup.  TIA

ROON > Ethernet > Zenith MK3  
Zenith MK3 > USB > M Scaler
M Scaler > DBL BNC > Audiowise OPTO DX TR
OPTO DX TR > TOSLINK OPTO DX RECEIVER
 
OPT DX RECEIVER > DBL BNC > DAVE

(VIDEO - M Scaler > OPT > TV)