Wow, thank you for such an in-depth response!! I really appreciate it!!
You nailed all the libraries that I used in this soundtrack. There's also a little bit of omnisphere in there, but only for a handful of notes.
For Medieval Battlefield, I recorded each part of the 3-part choir 4 times before layering the EW Choir over it. The mix is 40/60-ish, so you can probably hear the EW choir more, but the live vocals helped shape the vowels a little better. There are also low strings underneath, so I think that's the super-low stuff you were hearing.
I struggled with the mix of To Save Thy Soul a lot... the last few hours of composing was mostly me being indecisive of how much I wanted the solo parts to stick out at the climax point, which ended up with the accompanying string chords getting a little too soft. There was probably ear fatigue too, though. Definitely taking that percussive element advice, will apply in future works like this!