As someone who speaks four of those languages, I think I can assess this pretty well. Throughout the video it remains obvious that he is a native Swedish speaker. The Norwegian is pretty good, but it has a Swedish ring to it. The Finnish was surprisingly good. The Icelandic started out with a very noticeable accent, but the accent got milder as he kept speaking and was quite impressive. The Danish I have no idea about since Danish usually sounds like gibberish to my Icelandic-Swedish-Norwegian ears.
