Atm I do use my R1 with an Tokina 10-17 @12mm, doing 6 shots at 60°. 6 because I get the best results in PTGui. I came across other threads and the Canon 15mm 2.8. Now I thought why don't use my Tokina at 15mm.

1. The question I have is, what will be different from using 12mm apart from fov. Will I do get higher resolution because less overlapping?

Well I'd have to do nad. and zen. which was not a must at 12mm.

2. How would you set up the R1? At 0°, doing 6 shots, portrait + zen. and nad.?