The capacitor doesn't have a concept of "fast enough", it's a passive component. The signal is what determines what it does when it encounters the capacitor. Non-linearities and capacitor species aside, a good ole x7r 100nF would clean this up.

In general you can just liberally dump 100nF caps all over your pcb power traces and quash most problems like this before even knowing they exist. I joke that you make a circuit then take out your 100nF salt shaker to make it just right.

It's an easy test though and it can be an SMD component and some PUR-coated magnet wire or 30 awg single stranded kynar hookup wire.

Use a small amount of glue from a hot glue gun to fixate it when done, or epoxy if that's your thing. Avoid cyanoacrylate. Not always needed but I imagine a drone moves around alot.

Bodge wiring is a good skill to acquire - PCBs will not always be perfect. Maybe practice on something else first?

you can dead bug SMD caps

> If it's really 20MHz++ noise that's screwing him, you need something faster than a through hole capacitor IMO to deal with it.

That's always worked well enough in the past.