Re: Ring spacing?
The most important thing for the width is that it allows proper alignment during movement and so the straps don't get in your way. You want to be able to hold a support position (top of a dip), without the straps digging into your arms. A cubit is good, and I usually add another inch or two to that.
The width becomes less important as the distance from the mounting point increases. In gymnastics, the rings are hanging from 10 foot long cables, so the standard width works for everyone. But if you are hanging the rings from shorter straps, don't use the official measurement. Go with whatever is most comfortable.
Sorry for the long winded response. I hope it makes sense!