do bonus heroes and bonus buildings stack in aether mode?

Read, nino.

The buildings increases you fort level and thus your stats (or at least prevents them from being lower that your foe's stats)

Bonus heroes and bonus buildings do different things.

Including a bonus hero increases the lift you gain per match by 20, and the bonus unit gains extra stats like in TT.

Including a bonus building, whether on an offense or a defense team, increases the level of your fortress for that match, which translates into extra stats for your team or denying extra stats to your opponents.