Thank you for posting and welcome to the community. I would be happy to help with this.
There is no need to set a preset for the AUX input, you can switch to this using the AUX button on the speaker, or by choosing it as the input source on the Bose Music app and turning the input on from there.
You would not be able to preset the volume level of your speaker, but it will automatically start playing at the volume you previously had the speaker set to.
You can find more information on the features and functions of your speaker HERE.
I hope this helps. Let me know if you have any further questions.