if the rifle is "canted" it is tilting left or right, for closer "hunting" shots this isnt a big deal, but in long range precission having the rifle canted when that bullit leaves tha barrel can change you POI drastically at liong distances, even a few degrees with change your POI by inches!
and anti cant device is basically a little spirit leval that mounts to the scope or picitanny rail, for them to be truly usefull you need a bipod that can tilt.
as far as the rings go, other then asthetics, you need to have a good cheek weld and be comfortable behind the rifle its just as important as any thing else, on my 700 i run medium hight rings (same scope as you) and it allows me to have a good cheek weld and see threw the scope with out having to rack my neck on one way or another, if u find your self cranking your nect up to see threw the scope youd want to get a lower set of rings, chances are with a 50Obj, low rings wont work, so your stuck with medium or high.
