It’s perfectly fine if you used SM-2 before, no worries.
As for parameters, since parameters determine the exact probability of recall, they will also affect the graph. I can’t say how much, though, and I’m too lazy to switch to default parameters just to test.
EDIT: alright, I’ll do it for one deck
Well, either something is bugged or there is no (noticeable) difference
EDIT 2: ok, there is a difference, but I had to use a small deck to see it
It seems that optimized vs default parameters changes the total value on the graph by less than 1%