Everyone winds up with a preferred repairing position. I've repaired electronics and clocks on my lap for so many years that it's difficult for me to use a bench.
Bicycles are handiest to repair upside-down, and that works okay on a moped if you can ignore the carburetor and, prior to inverting the bike, spread a plastic grocery bag over the fuel filler hole and then screw the filler cap on top of that. That'll prevent fuel from exiting via the vent in the fuel cap. But mostly I work on mine while it's hanging from the rafters.