Imus products have a very spotty reputation for quality. They are are all subcontract manufacture (Imus does not own any production facilities, AFAIK
). This can mean significant swings in quality.
The "gaited horse saddle" is much more a marketing approach than a functional type. The idea that a "gaited horse" requires a freer movement than, say, a three day eventer or steeplechaser is just not true. EVERY horse in any athletic discipline requires free movement of the shoulder.
The position of the rider is going to fall into two broad types: a balanced seat or a chair seat. The balanced seat will put you in the middle of the horse with your feet under you. It allows free movmenent of the horse both laterally and fore and aft. It requires the rider to develop a good sense of balance and feel. The chair seat limits laterall movement, but permits a more "elegant" presentation and is very valuable for ropers, jousters, etc. In gaited horses it's used to "hollow" the back and give a more later, smoother ride. That can be problematical if the rider is not intelligent and skilled in their riding.
On balance, I'd avoid the Imus products. Quality is not assured and the promotion of the saddle is based upon hype, not science.