OK, so I went out and tested everything as follows based on the instructions of @xfacta. Specifically, I tried out three throttle based filters and one FFT one.
First of all, I set:
INS_HNTCH_ENABLE → 1
Then, for the throttle based filters I set:
FFT_ENABLE → 0
INS_HNTCH_MODE → 1
INS_HNTCH_REF → 0.075
Questions (mainly for @xfacta) the documentation does not mention a factor of 0.6 for INS_HNTCH_REF but says to set it to hover_thrust. My MOT_THST_HOVER is 0.125 so I set INS_HNTCH_REF to 0.075 as you suggested but where does the 0.6 come from?
You mentioned setting INS_HNTCH_ATT to 40. It was already there so no change needed but this is not mentioned in the documentation.
Finally, the documentation mentions setting INS_HNTCH_FM_RAT but you did not. I did not touch it but should I have?
Now, with these settings, I did three flights, varying INS_HNTCH_FREQ and INS_HNTCH_BW. Each flight was more or less the same, take off in Alt Hold, hard up, moderate down, hard up, moderate down, land. The idea was to stress the throttle somewhat.
Logs as follows:
Flight 1, INS_HNTCH_FREQ 37, INS_HNTCH_BW 37, log here.
Flight 2, INS_HNTCH_FREQ 74, INS_HNTCH_BW 37, log here.
Flight 3, INS_HNTCH_FREQ 108, INS_HNTCH_BW 54, log here.
Flight , INS_HNTCH_FREQ , INS_HNTCH_BW , log here.
Finally, I did a flight with FFT filtering. For that, I set:
FFT_ENABLE → 1
INS_HNTCH_MODE → 4
INS_HNTCH_REF → 1
Same flight pattern but I also did a bit of throwing it around in roll and pitch to record some responses, log here.
In terms of performance, there was not much I could tell by flying, all flights felt more or less the same (great really). What should I be looking at in the logs to make up my mind about which filter to select? Regarding throttle vs FFT, I am not planning on doing anything on the autopilot (Lua scripts or whatever) other than using it for flying. How can I compare the difference in CPU load across the logs?