Alot of difference, acceleration vs top speed cant have both.

think of a bicycle with gears.

14t front and 40t rear tops out at 110mph

15t - 40t tops out at 130mph so one tooth makes all the difference

125mph sounds about right in std tune, if you want to eliminate the speedo restriction issue the best way to go is with a speedo converter the "blue" ones are correct fitment for the nc30 and the speed you see will be recorded in mph now meaning your speedo can read to 190mph if that's what your clocks go to!
The most I ever got out of my std nc21 which had 59-60hp was 130 but that was sitting behind a zx9r and had slipstream effect!
These bikes arnt realy about top end there more about cornering after all in the real world where can you go at 130+ all the time, even in sprinting you won't have terminals of anywhere near that