Thanks for the checks, RagnarokCzD. Let me know if you find more, or remember where some other things were said.
As you can see (i was going to write hear ... but i really cant hear anything from there, so i had to turn subtittles on and see ... is is so awfully silent for everyone or is that some misstake on my side?) in that video you linked Swen said "in the Act 1" ... not "in EA".
Strictly speaking, yes. In the PFH Swen indeed says "[...] whether or not we're gonna put Level 5 in Act 1", not "in EA". Given the context (people having asked for Level 5 in EA for a while, people asking in the twitch chat during an EA promotional event), I feel it's relatively safe to assume he meant EA, not the full game's Act 1.
NickP said: "is not going to be available in Early Access at launch, we're planning to add it later."
Also i faintly remember Swen mentioning it in some PFH ...
I believe his words were something like "we were going to introduce multiclass when all our classes will be done, but we might just change our mind about that one" ... but dont quote me, i shall provide source once i find it.
Oh, worry not, I wasn't about to quote you from the top of your mind. But since you remembered enough of where it was said, I found it. It's in the same PFH, during the twitch chat segment. And in fact, immediately after the level 5 topic.
So what we know is that, during the linked AMA, Larian announced that multiclassing would not be available at the start of EA, but would come "later". In
PFH 3 (Patch 5), at 52:38, Swen reconfirmed the feature, and said it would be most likely be late during EA. But he also said he wanted all the classes to be available first. Now, many conjecture that at least one class could be kept for full release. And Swen said they'd maybe change their mind. So, maybe multiclassing will arrive in late EA indeed. Or maybe it will only be available in v1.0. Either way, it will be in the game, which is what I was really after. So I've rephrased this section.
Thank you for this very helpful post

Also, the Act 1 of v1.0 will be somewhat different from that of the EA version[...]
A good think to keep in mind. Especially for those who feel like some paths/quests are not fleshed out enough.
In my view, it's mostly something to keep in mind in order to keep some hope that the story will be a lot less lacklustre in the full game. But since Larian has not made any comment on a
specific issue with the Act 1 story (e.g. "the evil path sucks", about which they could have commented "we've received feedback on this issue, we've expanded/rewritten it, but we're keeping the change for the full game"), players should still provide feedback on the story.
[color:#FFCC00If you just want to experience the story and don't mind the lack of polish : no, see previous question.
I'm just going to note that it's still possible to enjoy an incomplete story. I mean...I did just that for 500+ hours of play time.
Ah ... yes. Certainly. By "the story" I meant the full story, but hey. I've rephrased this section a bit.