Long-time lurker, first post, but others who were there can confirm what I say. Most questions were about his writing process and other general topics. The only Cosmere-specific ones I remember were as follows:
Does burning cadmium actually slow down time or just slow down the perception of time? (there was a bit more to the question but I was on the opposite end of the room) The answer was it does actually slow time.
Is there or will there be a shard for Entropy? That was/is Ruin
There were a couple others with obvious answers (Is Odium the same person as Ruin?) but nothing else stood out. There was indeed a reading of the prologue to Oathbringer. POV character is
And for my own question while I got a book signed I asked "What would happen if you tried to cut aluminum with a shardblade and as a follow-up how significant is it that Nightblood has a metal sheath?" To which he answered, "It is significant, and a shardblade would not cut aluminum."