scorpions area a good investment.
I know ordering and repairing them is a pain but they are a nice controller.

If not then electronize. Heavier but repairable in the uk and usually people have some spare.

Asking if 20amps is enough for two drill motors. I would say try and get 30 to be safe. I have had drill motors jam from a big little flipper flip. Having one stalled motor can really put strain on the speedo.