Couple of thoughts...
UCL lenses offer 100+ extra lumens OTF, but are thinner and more fragile. Go with Pyrex for maximum durability. If you want to try both, just get extra lenses and request the bezel ring be loose installed.
ZeroRez are specialized parts with no length absorption. The main difference between cells will be the amount of force that is needed to activate with the the momentary boot. This pushes through the battery, against the stout spring of the Triple itself. You can expect something like:
IMR 18350 (short) - medium force
LiCo 18650 (medium) - heavy force
IMR 18350 (long) - max force
Output under LiCo will be the same. The regulated engine can 'pull' as much energy as it needs.
XPG engines are 6500K, with a mild blue and no green. Nichia are 4500K, with a smooth creamy white. Its about max output vs maximum color, but neither have a distracting tint. XPG2 engines will be 5700K.