Going to czy will?

Witam,
Która forma jest poprawna?
I 've decided that I will ,czy może I'm going to have a party in my new house.

po decided uzywa sie will, bo wlasnie podjales decyzje wyrazajaca swoja wole
jezeli usuniesz poczatek zdania z decided, mozesz napisac "I'm going to...', bo decyzje podjales juz jakis czas temu, a teraz komunikujesz swoje plany

Dziękuję :)

…or I’ve decided to have a party / throw a party… Mało kto ujmie “I’ve decided that I will have a party…”

???
(1) Don’t get near that dog. It will bite you.
(2) Don’t get near that dog. It is going to bite you.
What’s the difference? The dog's will differs from the dog's plan?

You know, Janski, there will always be aspects of usage of a particular structure or phrase that are not addressed by a given question on this forum, so you are always going to have something to add and thus tickle your inner sense of knowing better. Now, are you going to argue that the difference you seem to have pointed out with your examples and the difference the original asker was asking about is the same difference?