If you are interested in historically correct leathers in the 1700's to 1800's, then "veg tanned" is appropriate. The "ounces" scheme can be simplified as 1oz equal leather 1/64" thick, and 6oz is leather 6/64" thick.
For moccasins, you might try deer /elk hide, or Tandy's deer tanned leather. It will be soft and stay soft after being wet. Some sew a thick leather sole on to aid in comfort and durability over rocky ground.
Knife sheaths seem best with veg tanned, as it can be wet-molded to shape and stays hard. 6oz works good for me.
Shot snakes seem to need a fairly soft leather, so 2-3oz seems appropriate. There are other items shaped like gourds that are wet-molded to carry shot or ball. As best I can find, shot snakes are a mid-19th century device, and the gourd-like bags are hard to authenticate historically ... but they sure work great and look neat!
Oil tanned, chrome tanned, and latigo leathers are all great products but likely didn't exist in the 17th and 18th century.
If all you want is to make some leather items, you are best served by going to a leather shop in your area, getting advice, and handling yourself the product.
All the best in your efforts.
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