@sachman when _rate_bf_ff_enabled is enabled, the target response is shaped to achieve the desired (input) angle in a first order fashion (exponential). That is what the ATC_INPUT_TC parameter is used for. It is the time constant to achieve 63% steady state of the input. So with the default ATC_INPUT_TC of 0.15, then if you made a step input with the RC stick then it would take 0.45 sec to achieve that steady state.
When the _rate_bf_ff_enabled is disabled then the requested input becomes the target. There is no shaping in this case.
In the steady state, they will be the same. The difference would be seen in how they achieve steady state. Hopefully this makes sense.
Regards,
Bill