First, consider the recording setup. The microphone and recording environment are the biggest factors affecting audio quality, and it's worth asking participants to think about where they can record - a quiet space with soft furnishings or curtains works best, as this will help to avoid reverberation and echo.
If participants are joining on a computer or tablet, try to avoid a speakerphone setup. We use echo cancellation in RINGR to ensure that you can do this if necessary; however, please ensure your participant doesn't have their volume set too loud, or uses headphones during the call. It's always a good idea to have a quick 'sound check' in the Green Room before you start recording.
Obviously, sound quality can be further improved by using a high quality audio equipment, such as a headset with a correctly adjusted boom mic, or the Apple earbud style headphones with an integrated mic - these are readily available and come with most smartphones. RINGR usually recommend mics from IK Multimedia, such as the iRig Lavalier mic or the iRig Pre, which will allow you to connect a studio condenser mic with XLR connector, and will also supply phantom power.
That said, RINGR desktop will support any mic/headset you can connect to your computer, including TRRS mics that plug into the headphone socket on your mobile, or via the lightning port on iOS devices
Finally, there's no need to worry about any RINGR settings for the audio format. Any versions you need can be created after the conversation.