As far as balancing spinners, yes you can do it on a good quality balancer. I've never bothered though.

Remember, the effect of being out of balance is going to be a weight * distance thing. So being a little bit off on a long prop is much worse than being more out of balance on something close in, like most spinners.

that's not to say that you shouldn't balance the spinner, just that many of us don't, and usually the world doesn't end as a result. If you do a pretty good job of getting the cutouts the same size, you stand a good chance of being close enough.