Are you able to continue exploring after seeing the actual ending and credits with Thor?
I actually won't, because I really dislike two things that they changed in the game world after the end credits:
1) My buddy Jörmungandr is gone from the lake. I really loved him chilling in the background.
2) I don't like the much colder and more desolate vibe of the world after the winter set in. I really liked the bright, blue and cloudy sky as it was before.
So I am probably going to wait until photo mode drops, hopefully within the next couple of weeks, and then I am starting the game again. This time I won't finish the story before exploring all of the world in it's much nicer state.