You can finish the game on 100% before the ending, I think. There are 2 optional areas with arena like challenges and than something else, little bit grindy, bud rewarding and pretty entertaining not only gameplay and design wise. Other than main story - lots of collexlctibles (some being very cool), challengikg valkyries fights, some unbeaten hard enemies and like 18 (not sure about thr number) "holes" to other dimensions, half of them being "traps" from where strong enemies come from. And on top of that, exploring areaa you didnt visit until then and entering locations you can unlock just after you gain some skills and so on. You need to backtrack and its a little pain in the ass (locked areas that you can travel through just by fast travel) and still have to walk from the end of one area to its start if there isnt fast travel doors in its end.
Backtracking kinda sucks, other than thay, post game/side quests/errands/exploring is magnificent. Shame there is not more. I constantly had this feeling: Damn, this could be witcher 4 we never got after wircher 3 (in that genre).
Here to some dlc/content for at least 10 hours.
corybarlog if there is any chance you read this, everyone who buys your game will have the need for more. Its more addictive than horizon and while horizo felt full enough with its 40 hours, gow (with the same amoun of time) feels like there should be 20 hours od content more. Its just epic. I might give it a full 10/10 after second playthrough/adding NG+