Currently, you can set a default Theme in the plugin settings, which will apply to both Tabs and Accordions display.
It would be nice if you could instead have two settings, eg. "Tabs Theme" and "Accordions Theme", which would serve as default themes for their respective displays (unless overridden in the tag).
For example, being able to set "Pills" for the tabs, and "Neutral" for the accordions. I'm not sure if it's possible to apply the theme change when the automatic switch from tabs to accordions happens (viewport), but it would be cool to at least make it work when the {accordion} tag is used specifically.
For backward compatibility, you could make sure that both these settings inherit their value from the previous generic "Theme" setting.