Garageyears
Left-seat/right-seat - pretty much everyone reading this post has a mouse sitting just to the right of their keyboard I'd bet. Switch the mouse to the left-side and leave it there for the rest of the day. For the first few minutes things are a little 'confused' - 4 hours later it will feel normal.
Not everyone. I'm left hnaded, but have extreme difficulty using the mouse/trackball/touchpad with my left hand. In 50 years of flying, I've never had problems with a yoke or sidestick from either seat. Go figure.