Can QLab send OSC to the X32? Absolutely
Set a static IP on the X32 and link that up into QLab (Port 10023).
Then follow this protocol guide to assist you (which is sounds like you've looked at).
One gotcha is that if there are more than nine channels (i.e. 32 channels, but only 8 busses) you have to put a 0 in front of single digit channels. Meaning to mute channel two, you would make a new OSC cue with a custom message that would like like this:
/ch/02/mix/on 0
And to turn it back on:
/ch/02/mix/on 1
If it helps you decipher the protocol guide, these commands came from page 10 ( /ch/[01..32]/mix/on ) which then states that it's an enum (ON,OFF) which means you need to send it a 1 or a 0. ( /ch/[01..32]/mix/fader ) level [0.0...1.0 (+10 dB), 1024] would mean that to set a level, you need to give a value between 0 and 1024. On page 14 you'll find the settings for the main fader.
Hope that helps!
As for OSC and MIDI simultaneously, I don't see why not. I've never done both at the same time, but don't see why not.