This probably would have been a better choice point heading into the final arc. ( I also have a massive nitpick regarding the lack of my camp companions in the final arc, you're telling me they would not help out and be with the allies? no, that's dumb.) Taking sides would most certainly either lock you out of later choices with the brain, or force you to end up in another fight, as i can't see Orpheus being supportive of you dominating the brain and not destroying it.
In one of my playthroughs I did only enough tadpole stuff to kick off the dreams, but consumed no tadpoles at all, and did not take the astral tadpole (I have a fun collection of all the tadpoles i've picked up but not used), but this didn't really do anything in regards to changing my options. It would be nice if were offered some more approaches to the final arc.
Maybe Orpheus being Githzerai.
If Orpheus is actually the direct son of Gith like Larian state, he's from a point around the Gith and Zerthimon major split, before the pact with Tiamat, where the difference between the two people was still philosophical, before a millennia of dogma and living in two separate planes. He'd still probably call himself a Githyanki (literally "followers of Gith"), due to his philosophy, but he's much closer to what the Gith were before their racial split.
I also wanted there to be more Githzerai, when the Gith monks showed up i thought they might be, as the Githyanki aren't as ascetic as the Githzerai and mainly produce warriors, not monks.
