I’ve solved my issue (and possibly yours)! The responsiveness of the text in the dropdown is inherited from the site style. For me, making changes to the site style (Scale Text on/off) have enabled me to control px / px* for the fonts in the dropdown. After making the changes in Site Styles, you may need to toggle the font between site styles to get it to update. Unlike elsewhere, it doesn’t look like you can override the Site Style settings.