I have weird brain wiring of some kind. I'm not lefty, righty, OR ambidextrous. I do some things lefty, some righty, and I CANNOT switch. When I played baseball as a kid, I threw righty, but batted lefty. I play guitar righty, but write lefty. Etc. I'm actually researching this right now for a feature story I might write on this whole phenomenon. I'll link to it here when it's published.
As for guitar, just as with everything else, I can't imagine trying to play lefty. When I try it, it feels as clumsy is it does when I try to write righty or throw lefty. I have always felt a bit more dextrous with my left hand, though (on guitar), and I tend to be a bit sloppy when fingerpicking with my right hand - which might be why I hesitated for so many years before delving into it seriously .