The different feel from NG to classic is due to the different types of feedback springs fitted to the brake pedals. A lot stiffer springs on NG.
To disconnect autobrakes by using pedals, it will take manual input equalling approx. 800 psi, regardless of NG or classic.
The sensation of acceleration after the manual input only indicates the autobrake system is applying a pressure GREATER than 800psi.
If you feel the brakes grabbing, which most people end up doing, the autobrake system is providing the set deceleration rate in conjunction with thrust revers that requires LESS than 800psi onto the brakes.
Rotating the selector from any setting to OFF is fine, but you do run the risk of applying 3000psi immediately into the system if you by accident select RTO above approx. 60 kts GS.
The aircraft will then have a nice imprint of your face with a very surprised expression on the inboard ND
Disarm the system by slowly stowing speedbrakes.
If you do not NEED to brake above 100kts, leave the autobrake to OFF!
Settings 3 or MAX is to be used when conditions demand, meaning limited wet or contaminated runways, strong crosswinds or low vis.
Anything else is waste of money and good brake disks.
We are talking steel, not carbon here.