Well, we have different classes....
Stock is usually a spec motor, typically a 21.5 or 17.5...sometimes 13.5 turns....
Modified is whatever ya want, as long as its an approved 540 size motor. So as long as it meets the size dimensions and has gone through the approval process, its legal to race with, so if a 700 watt motor exists, then you can run it....honestly there is more than enough power for any mod class really at this point, most of the testing would center around spec motors (10.5, 13.5, 17.5,21.5)...though using the dyno for mod stuff to help with gearing and stuff is helpful.
1s racing is 1 cell lipo racing..........while most other classes are 2s (2 cell). So 3.7 volts 1s, and 7.4 volts 2s. 1s is only really used in a few classes for onroad and oval......
Later EddieO