I have finally watched the audio commentaries from the 4K movies (which had a release in 2024)! There is a good amount of it that I'm still unsure of, as some of the stuff is said jokingly (though one thing I thought was a joke and thus didn't bother taking photos I later looked into and turns out was mentioned in Final Drill), but there's some very interesting stuff in here...
In response to the rest of the crew saying that Spiral Power is a feeling, Nakashima (I think) says that Spiral Power is tied with the quantum mind hypothesis, in which the mind is connected with outerspace via quantum entanglement (I'm not sure if this is a joke or not, but it actually is pretty consistent with what we know about it, given Spiral Power does draw energy from galaxies in other dimensions).
Arc Gurren Lagann's Space-Time Shattering Burst Spinning Punch is said to contain the force of multiple universes.
After Super Galaxy Gurren Lagann drew the real Moon out of a pocket dimension, there were two moons around the Earth; thankfully, Super Galaxy Gurren Lagann was able to counter this as Spiral Power can do anything, and the gravitational force was shifted so that it spilt out into different dimensions and didn't mess up the Earth (this may be said jokingly, as there is lots of laughter accompanying this statement, and the main story of the show does have the 'Moon' exceeding the Roche Limit, something that's mentioned by Final Drill; at the same time though, it's more than possible for Super Galaxy/Cathedral Terra to have some kind of Roche canceller, and we do see artificial gravity on board the Super Galaxy, plus it has the ability to drag things across and travel between dimensions, so it's all worth keeping in mind).
This as far as I know is the only audio commentary from the creators with English subtitles. It is not, however, the only audio commentaries of Gurren Lagann (infact there are other Trigger series which may have some interesting commentaries such as Promare). Tracking them down and translating them will be trickier, but I've come this far, so why not keep drilling?