depends on how strong they are
most 20 man teams are very casual or very new
therefore are typically pretty underclassed
which makes it easy for a team of 20 strong members to outclass them and go undefeated
it’s been done before.
Active/competitive alliances capping member counts can allow them to find a bracket and use it as a stomping ground to chain wins
some alliances slowly climb members until they find the sweet spot, some drop members until they find the sweet spot
you’ll see tip top teams hangin at 29 members for this very reason and if they see an equal team drop to 29, they’ll drop to 28 etc