What type of oil is used in korean side dishes?
Toasted sesame oil is usually the go-to for Korean cuisine. It is included as a seasoning in the last steps of the recipes you link.

Sesame oil is typically used for seasoning, not cooking with. Some types of sesame oil may be appropriate for stir frys and such, but I don't think I've ever used toasted sesame oil (the very strong smelling, flavored one) for that kind of use.