I use convection bake for pastries, breads, casseroles, cookies, pizza on the top rack.

Non-convection bake for delicate baked goods such as cheesecake or any delicate thing that requires a water bath.

Convection Roast for well, roasts, (feel dumb typing this). But essentially large cuts of meat, poultry, whole or cut.

I don't have non-convection roast and am not sure I would use it if I did.

I don't have convection broil either. But since broil implies heat from above how does convection broil make sense?

I guess my GE answers most of the questions you are asking.

In summary, I use convection when I can except for delicate things that contain eggs.

HTH
GeeB