All of it.
Previous titles had full VO, aside from protagonist(s). I would assume it will be the same?
They said they can't do it this time?
Where and when?
They have more budget for this than any other Larian game so far and they went for a close up cinematic camera for dialogues here.
It would be pretty absurd to claim the intent to save money in an area where they didn't in the past.
I thought theh said they couldn't possibly voice everything?
You are probably just thinking about voicing all the possible permutations of the main character.