My apologies. I meant the mythos 9 last night instead of the 7. The 9 has 4.5 inch drivers. You are correct that it is best to match driver sizes.
I would pick option 1 of your choices. The front soundstage matches in driver size. Which will be best. And the surrounds aren't as important so you could get by with the standard gems having a smaller driver.
I personally do the same thing. Except from 5.25 in the front to 4s in the rear