The euros format would slap for champs
the groups make sure the best teams are through, and then single elim all the way through starting at the Ro16. Champs is supposed to be all about the culmination of the whole year, I don't think there should be second chances. It would make the matches much higher stakes and entertaining.
Alternatively, employ this with smaller numbers for masters and then keep champs at groups -> double elim. Overall either of these changes would just make Masters and Champs different outside of branding and prize money. Either I cooked or not, thats for you to decide