There seems to be a strong correlation between drumming and ND. Drums were my first love because focusing on rhythm was always much easier than trying to learn chords, even if at first it seems like you're doing a lot of new things at the same time. Would highly recommend, and there are so many types to choose from!
Also, the guy isn't autistic but The Flashbulb (a semi-popular musician) taught himself how to play guitar completely upside-down due to his left-handedness, which always seemed so cool to me. I'm fairly certain he reads music like normal and can do all of the usual things, all the while playing a right-handed guitar upside-down. It can definitely be done in many different ways, and with the right amount of confidence nobody will be the wiser!