In the spell description for Wind Walk, we see that
The only actions a creature can tale in this form are the Dash action or to revert to its normal form. (PHB p.288)
There are no explicit restrictions mentioned aside from that. Also note that
Anything that deprives you of your ability to take actions also prevents you from taking a bonus action. (PHB p.189)
However, Wind Walk does not exactly stop you from taking actions; it limits your options to the Dash action. It's not clear to me if the effect qualifies as depriving the creature of its action.
Additionally, reactions have no such limitations as far as I can see, so even if bonus actions are not prevented, it seems as if reactions are fair game.
The PHB also lists several potential "free actions" (p.190) that the player may take on their turn.
It seems to me that these things may violate the spirit of the spell, and I would probably rule that creatures under Wind Walk could not, for example, make opportunity attacks, use Wild Shape, cast spells, or otherwise interact with the world in a way that wind could not. However, my curiosity has gotten the better of me.
Is there anything in the rules or errata that specifically forbids taking bonus actions, reactions, or "free actions" while using Wind Walk?
Best Answer
A bonus action is an action
PHB p. 189:
A reaction is an action
PHB p. 190:
Other Activity on your turn is not an action unless your DM says it is
PHB p. 190:
Wind walk limits what you can do with your actions: be they normal, bonus or reactions. If you can dash with your bonus action, you can Dash twice on your turn (i.e. move 3x your speed).