It is SO hard to say "how hot", it is so subjective. The main thing about Korean chili flakes for kimchee is that it has no seeds. That said, in absence I have used just about everything you have mentioned, except the Chinese chili in oil I think that my best luck has been red pepper flakes; that's closest to the pepper I've bought that is produced for the purpose (I've also used Vietnamese chile garlic sauce). The Korean kimchee chili I've bought at Asian markets was not a powder, but the flakes minus the seeds.
As I said, the heat is up to you. This isn't something you make now and eat in an hour. Go modest, let sit for a day (enough for the chili flakes to reconstitute), give it a taste. If it isn't hot enough, then go ahead and add one of the chili powders.
Some of the Korean stuff is knock your socks off. The last bag I bought was very mild (remember, subjective ... to me) and I wound up adding chili powder that I think was from India, to heat it up.
All of the Koreans I've met and shared Kimchee with were in this country and had lived here for years. They made kimchee out of just about anything they could find. Most interesting was one made from boiled potatoes . Think a very, very zippy potato salad. Least favorite are the fishy ones.