While I don’t play ck3 I have played a lot of Paradox games. Unfortunately the reviews are useless, most are based on “I don’t want to pay (this much) money”, which is fair but not relevant for the content.
It matters for most, and if it doesn't matter, then you would probably just buy it regardless. It's always additional content, and probably worth it to you if its cost might as well be 0.
the tournaments one is very well reviewed. The Norse one is worth it if you want to play the Nordics.
Royal Court is mostly only good if you want to make the game easier (you get lots more equitable artifacts etc). It sounds like they are improving this to make the actual court bit more interesting.
The event pack/friend and Foes are normally considered not great, possibly even negative, but it sounds like they are updating them to fix the event frequency.