How do I adjust Homepod stereo balance?
Other than moving your speakers around about all you can do is play with the balance and the equalizer to adjust the sound to your liking.  There is a free app named eqMac which lets you apply an equalizer to your mac. It also has sensitive settings for the balance. You can adjust the balance to get the appropriate settings for your home pods. Maybe this balance adjuster does a better job than the internal one.