Hello and welcome to Apple Support Communities helppp_11,
I see that you're having an issue with the level of volume coming from your Mac after disconnecting your AirPods. I'd be happy to look into this with you.
I know it's important to have your Mac working properly, so let's have you try some steps to isolate this issue you've been experiencing. First, restart your Mac and test to see if the issue remains. If the issue remains, try starting in safe mode and testing again. If the issue remains while in safe mode, try creating a test user and testing once more. The articles below will guide you through those steps, if needed.
How to use safe mode on your Mac
How to test an issue in another user account on your Mac
Let me know how this goes and if you notice any changes.
Have a great day!