It has nothing to do with being right handed or left. I'm right handed and play RG with my left mostly. It's all about what side you decided to go to that first day of rubber guard. The second day you will automatically go to that side because you already have put in reps on that side. My right leg in RG has to work equally as hard, it just has a different job but it's doing that job with 100% of it's power. The same goes for arms and hands, if doing Jiu Jitsu correctly all your limbs should be working equally hard even tho they have different jobs :-)