If you are doing well in 6 right now, 4 should be pretty easy to do. Also, the AP classes you will be taking are (except for Physics C) much easier than the ones you are doing right now. Yes, Physics C is hard but you seem to be doing well in your AP science classes. Since you have already taken Physics 1, Physics C shouldn’t require as much studying which will free up time for college apps. World just got so much easier because of the change to “modern” and is basically half the length it used to be. I personally think that you can start studying after college apps are in (defo start them in the summer) and still get a 5, especially since you got a 5 on euro which is generally considered harder than world even before the modern revision.