The Outputs on the T4, including all possible outputs

[sugarplumsss]

Normally I use the two Main outputs.
Through lack of knowledge, I ask, does the L/R Output and the R output, have to be conceptualized  this way:
L/R boils down to Left side
Right, to Right side?
This has been my assumption.

But on one particular job, I had to reverse this. And frankly I did not notice a difference. I have historically only used headphones to hear T4 at home.
The various options for outputs, seems to suggest I need to setup the PA in my living room. I am now willing to do this. Due to pressure of being on a job when possibility of experimenting with outputs, is nil... I remain ignorant of the Outputs, and for last 11 years only use the two main outs.

A new situation has arisen.
My new bandleader has his L1 Bose to my Left
In essence I am playing through his monitor
This means when I need more drums, HE has to hear the drums louder than he wants.
He strongly urges me to give him BOTH Main Outs; saying they create a fuller stereo sound, as opposed to just one Output. I think, to my surprise, he is correct.
He explained- the Single Bose L1 speakers, reflect a stereo field, because half of them are angled in one direction, and the other half is aiming in a different direction. Kudos to Bose, a great company in my experience.

I absolutely need a speaker to my right.
This brings up an option I have not checked, until "tonight" ( actually yesterday ).
I tried the Sub outs earlier this evening...
I failed at using them. Missing parts seemed to be the case, but I was pressured to get up and going ( Heavy traffic on this evening ) and abandoned the Sub Out as I had hoped.

The idea of assigning different parts to these Subs is appealing ... I can hopefully get more drums and bass in my mix ( Sub Outs ) without overwhelming him.  Also, can I assign ALL PArts to Sub Outs? Or ANY combination of parts in the two Sub outs?

The Sub outs are a mystery to me... As much as you can offer ( links etc ) by way of explaining the 2 sub outs.. the headphone out!! the Aux sends , and any other potentially useful outputs on T4, Plus the Output assignment Page in the mixing Console - (the furthest page to the Right of Compression ) would be very helpful.
Thank you

[sugarplumsss]

The Reference Manual offers sparse info on the Sub1 Sub2 Aux stuff.