I don't think anyone has ever recommended instant PWO since you gain little nutritional value from the added sugar.
Oats are medium - med/high GI (except for steelcut). A lot of people don't use oats and a lot of people do, try it and see how it works for you.
The oats you want are quick oats (the 3 minute stove/ 1 minute microwave variety) or old fashioned rolled oats.
The fat from oats is minimal in slowing things down.