Exactly so! Smaller master cylinder bore will generate higher brake line pressure, but will result in longer pedal travel. So there is a limit to how small you go, you want to have some extra room before the pedal hits the floor since you'll need more travel when things start to get hot
Yup, that would be an even higher line pressure than the 15/16", with slightly more pedal travel. I haven't used one on an A-body but I'm sure that still leaves plenty of pedal travel in reserve.
Sounds right, I think the Diplomats/5th aves used a 1-1/32" in a similar package. DoctorDiff sells those as 1-1/32", or sleeved down to 15/16" (which is what I use).
1-1/8" would be a pretty "high and hard" pedal though. Factory sizes for these cars were 15/16", 1" and 1-1/32" depending on the year and brake set up.