Something that lets me select a frequency above which all sounds would be filtered in real time? I don’t know if a software can separate the high pitched sounds from the rest of the sounds. If it was possible that would be perfect. If not just removing all sounds when any sound goes above the threshold.
If your goal is to lets say, filter frequency under 200 Hz to filter keyboard noise, equalizer APO would do, it is better than OBS Studio plugins because it uses a driver which works at lower latency without disorientation.