Re: how many lefties use a RH bolt rifle
Handedness and eye dominance are both over-emphasized.
I am naturally left-handed, but right-eye dominant.
I grew up shooting pistols right handed, and rifles left handed. A few years back, when I got back into competitive shooting, I decided to shoot rifles right handed, because shooting a right-hand bolt gun left handed is inconvenient if you have to reach over an optic to cycle the bolt.
Now I can pick a rifle up with either hand, and shoot it that way with equal facility. Same with a pistol. And I shoot both sides with both eyes open.
Eye dominance doesn't much matter with a rifle, because your cheek weld lines you up behind the sights.
And it doesn't much matter with a pistol, either. Larry Vickers, who has won national championships, is right-handed but left eye dominant. Line the sights of a pistol up with either eye - it doesn't matter which one - and the bullet will hit the target if you press the trigger correctly.
For someone who had never fired a firearm before, I would probably encourage them to learn to shoot a pistol with the firing hand on the side of their dominant eye.
Otherwise, it's not a very interesting thing to worry about. Learning to shoot correctly is far more important.
Added: running the bolt of a right-handed rifle with your right hand while shooting left side works fine if you don't have to support the rifle. If you're shooting unsupported, it doesn't work so well.