What we need to do for the 100% ?

Do all the quests ? Collects all the collectibles ?

Since there's no ingame percentage counter(That I've found) I guess it's up to you mostly. I mean there's the challenges and the achievements and the collectibles, but I don't know. Try messaging Nord about it (Truljin on Twitch)

I did realise there wasn't really a set rule thing but wasn't sure what to set it as myself :/

Maybe have a AllQuest% and a Collectible% instead? Or use 100% for both of these in the same run

A MaxLevel% could also be fun I think

Where are you guys looking for the percentage tracker? The only one I can find only tracks the main quests.

The 100% category has been officially defined now