The channels of the respective output format (2.0 / 5.1 etc) are exported as separate mono audio files. Usually the encoders (DCP / Blu-ray Etc.) expect separate audio tracks as input.
Apart from that a cinema mix needs to be mixed in a certain dynamic range similar to ebu r128. Check I.e. this video for an introduction:
There are a number of sources you can look into but not all of them are accurate. David Sonnenschien is great for explaining how to set up projects, how to analyze your script, how to create transitions, evoke the emotional energy of a a sonic landscape etc. Other good books or websites are:
The Foley Grail
I'd say experiment with microphone placements, different types of mic, condenser/dynamic/contact and mix them together to create large than life content.
Here's my suggestions on mics to use for foley work:
AKG D112 - Bass drum mic, good for big boomy sounds.
Sennheiser - MKH8050 & MKH8040 General all around cleanliness, low noise and can take high ...
There's also an article in Mix Magazine from the year the film came out. It used to be up on their website but it's not there anymore. You might look around for back issues.
All of the cinema spot mixes I've done over the last couple years require the mix to be at broadcast levels. It used be that we delivered leg(m) mixes but at least for NCM they now ask for a broadcast -24 lufs mix.
Who are you delivering the mix to? Are you actually doing the mix or just sound design?