Braiins OS+ doesn't control the hashrate, it controls the power used. Within this power limit, the resulting hashrate will vary according to the state of each chip, finding the most efficient solution. Absolutely different to whatever any modder does.
Yes, you could change this power usage at will. If you stop the mining, only some power from fans and the control board is in use, which is about 30W for S17.
Bitmain PSUs had? a hidden feature to turn them on and off if you solder a couple of wires to a switch, not sure about recent models but check this:
https://support.bitmain.com/hc/en-us/articles/360012411694-Introduction-to-APW3-Gently remove the resistor (if there is) on the signal point "-" and "ON". After removing, lead the wire to each point (in total you would need two wires), connect the wire to your remote device and the PSU can be switched on or off remotely.