Wotja V21.3+: These versions support dynamic switching of the audio output device meaning a restart is not required after the setting is changed.
This short video shows you how to configure the Settings in both Wotja V20+ (i.e. also applies to V21) and/or AUM/Audiobus so as to avoid audio noise/distortion/glitching etc. Although the video was created on iPad the same principles apply to iPhone and any other iOS app that can load Wotja as an IAA.
NB: The video focuses on the *Samples/Frames/Block Size* setting as that is the most likely cause of noise issues, but the *Sample Rate* in all apps must also be the same, too. Note that in Wotja V21.3+ a restart is not required after the setting is changed as these versions support support dynamic switching of the audio output device.
The video was created on iPad 10.5 with iOS 13.3 and Wotja 20.0.2