go to their website and see if they list the specs on their rings. also check out Brownell's and MidwayUSA. Brownell's lists the specs in the listings on the products they carry. MidwayUSA has a applicatiion chart listing many different scope rings with their specs based on which to use with a particular scope size.
and yes, the closer to the bore axis the better. having the scope down lower helps make a more consistent cheek weld which means your shots are going to be more consistent and helps in accuracy.
i too have a hard time with rings and sometimes will end up ordering another set or different brand to get the proper clearance with a particular scope.