For a BWR, the feedwater control is (or used to be) a 3 element system. At full power, the control system generally sets feed flow to match steam flow, with level error serving as a correction factor.
There really isn't a "notch" on the pump controller. As I recall at Perry, the original manual speed control knob was too coarse, so they changed it to one which took twice as many turns to get to maximum.
I recall the feedpump flow instruments as being 0-25,000 gpm per pump, with major increments of 5000 gpm, minor increments of 1000 gpm.
Total feed flow was something like 37,000 gpm, and the control system could maintain level within about +/- 1 inch, with one inch of level in the reactor representing around 200 gallons.
In the event of a turbine runback to something like 40% power, the feed control system could maintain reactor level within limits (call it a reduction in feed flow from 37,000 gpm to 15,000 gpm in approximately 30 seconds).
This is all based on memory, from a long time ago, for the original analog control system.