I think so, yes. Route both L and R to one matrix bus, and assign that to Out 1.
That depends on how you provide a signal to the Out port: Out 1-16 is just the output assignment. You set the volume on the channel that feeds the output. This can be the mains, but also any of the buses, an Aux bus or a matrix.
You're comparing apples and oranges:
To make sure you've got the USB interface set to 32 channels:
Setup menu, Card tab:
set to 32 in/32 out.
To connect the USB input to the 32 channels:
Routing menu->Home tab:
this is a list of possible inputs that can be assigned to the channels. This is done in blocks of 8:
In the input 1-8 column, select the row 'Card 1-8'. This assigns channel 1-8 of ...
I had this same issue and what would recommend and what worked for me is make sure the two boxes by the bottom are checked when setting up your driver in reaper! Especially the (Ignore asio reset messages, needed for some buggy drivers) box
I just wanted to add a bit more details to Michael's answer regarding how to make it work with the UFX1204. I know it's 5 years later, but the manual doesn't properly address this trick.
First, send channels you want to hear effects on by turning their individual FX knobs. Press the FX ON button as well in the MULTI-FX section.
Then send everything on the ...