It seems like a steal. And it is a steal(but legal).
Your 10s5p pack should output 1850w(50amps) and the 12s4p pack at a lower 1776w(40amps) nominally. When fully charge you can expect a 13% increase in peak performance.
I usually ride at a peak of 400watts but start-ups can get up to 1200w. I use a single 6374 170kv motor at 1/3 gear. As long as you aren’t on a dual 6355 setup blazing 35mph, you are fine.