The "canting" feature on boots is really an adjustment for accomidating curvature in the lower leg (tibial varum).
In EXTREME cases you can address tracking of the knee using this feature but the range of adjustments is usually so limited (typically +/- 1 to 1.5 degrees depending on the brand and model) that no real "canting" can be achieved.
Without a properly supported foot (i.e.footbed ) this adjustment is virtually useless. As the foot goes in and out of pronation the tracking of the knee changes, in some cases drastically.
A well constructed footbed, no matter what brand is always the first step in addressing alignment issues. Once the foot is held in a reasonably stable position true "canting" needs can be determined.
Ideally for most recreational skiers about .5 degrees to 1.0 degrees of internal knee tracking is appropriate. This helps you transition to the inside edge but doesn't lock you on the inside edge. True performance skiers will probably favor closer to 0 degrees but you never want to be tracking to the outside.