I believe there are ways to accomplish most everything you’ve mentioned (unfortunately, I’m not in front of the H90 now). Self-oscillation, so … Bouquet Delay? You can MIDI map to PERFORM 5 or 6 (wherever you have it placed), or directly with press & hold on the appropriate LED.
For another delay algorithm, you can often achieve self-oscillation by binding to (goes to 110 / maximum) FEEDBACK controls. I’m a fan of repurposing the three Perform Page 2 HotSwitches for multiple parameters, across both A & B Presets. MIDI-mappable.
