The levels of the Archons are what will be playable. There is a max level and minimum level for each bracket.

So in Bracket 1, every Archon will have a level 1 limit, no matter the level on the card.

Conversely, in Bracket 3, you can play an archon at any level between novice and Silver level (5,4,3,2). Anything above this range will be nerfed to the top of range.