What are all the requirements for campaign progress?
Do I “only” need to do all achievements? Or there is more “other” requirements?
All I managed to google so far is that I need to complete lost viking 500k points achievement for 100% terran campaign…
You have to do every achievement under the Wings of Liberty, Heart of the Swarm Legacy of the Void, and Nova Covert Ops. This does not include the 10th Anniversary achievements. But it does include The Lost Viking achievements as well as the Masters achievements that aren’t listed in the mission briefing.
If you go to the Achievements section in your profile you can look at what you still need to complete.
That might be a stupid question, and I think I know the answer, but is brutal also required for 100%?
Yes. You have to beat every mission on Brutal for 100%, including alternate missions and the secret mission in Wings of Liberty. So for the Nova/Tosh, Selendis/Hanson, caves/platforms choices you have do the other choice on the Mission Archives.