Hello ashandecosta,
Thank you for posting in Apple Support communities. We understand that you are wanting to know if a third party app on your iPhone can use the mic from your bluetooth headset. We would love to help you with this.
As long as your bluetooth headset mic works and is connected to your iPhone that the game is being played on then the mic through the bluetooth headset will be used primarily.
This resource can help you pair your bluetooth headset to use with your game: Pair a third-party Bluetooth accessory with your iPhone, iPad, or iPod touch
Thank you for allowing us to support you.
Have an awesome and productive day!