I’ve never heard of refined oatmeal, so I think you’re clear whatever version you buy. However, there is variation in the glycemic index among different preparation techniques, if I remember correctly. Steel cuts are the most slowly digested, followed by rolled oats, followed by instant. But regardless of the type, you’re still getting the whole grain with all the fiber.
If you were ever unsure about a product and want to check, just look at the fiber content to confirm you have the whole grain. I don’t think you’ll find a low-fiber oatmeal.