I am curious if you notice a difference by resetting the trans first instead of just adjusting the final gear and then top speed.
There's no difference from my experience, when a final is chosen, then top speed is changed, the values presented for gear ratios are still presented as preset range ( the same value range whether the transmission was reset or not ). On race cars with only custom transmission available, this can be easily tested. I wrote about resetting just for the sake of me being cautious.
What makes a big difference is power upgrade parts that increase engine rpm range, like engine tuning, sports computer, exhaust and catalytic converters.