If you ignore Ep2, you can see renders are increasing as the Paths are created. That answer the question "why our choices don't change the story too much?"Image count per Episode/Day (from image folder properties) :
Ep1 : 213
Ep2 : 505
Ep3 : 338
Ep4 : 481
Ep5 : 1074
Ep6 : 1052 + 973 + 1014 + 441 + 507 = 3987
So dev created almost 4 times the content for Day 6 (3987) compared to Day 5 (1074). Still if you assume that every one of the 18 paths gets roughly the same amount of content, that is only ca 3987 / 18 = 221.5 images per path for Day 6.
But I wonder why ep2 have so many renders?