Resetting the ECU only clears stored error codes.
It does not in any way effect engine operating paramters.
Your ECU is constantly learing
as you drive, making adjustments to the engine operating parameters to achieve optimal performance and keep your emissions level correct. There is nothing you can do to change that.
That information can be found in the factory service manual or the Haynes service manual.
A complete cycle is a start and run up to normal operating temperature allowing the ECU to go into closed loop mode. (reading your o2 sensors and making adjustments to the A/F mixture) It takes quite a few clean runs, ~30 with no errors detected to clear a stored error code automatically. Your check engine light can clear itself.