Talking about the ground issue: I found that the USB connector is able to power an Arduino or ESP8266, with common ground. So, would doing that and leaving out the ground clip entirely be a good idea? I guess starting at some frequency, you want to keep the loop small and use the short ground clip wire, but for a lot of stuff, this should work, shouldn't it? It wouldn't be the first time that I have a hard time finding a good position to place ground on a miniaturized µC board.