question: Do you think this will work well with the potential future work of height params with Advanced Layouts? I suppose if we were to introduce such an API, this would become the default maxHeight, and any overrides from the user could take precedence, but wanted to hear your thoughts on this.

Think this could be easily adapted for a potential height param, as you noted would just have user-specified height take precedence over this default maxHeight, but still makes sense to me to have some default (in this case 4 options tall).

Also, currently working on tweaking this from a hard-coded value to a calculated value in rem based on baseFontSize & padding values to better integrate with adv theming 👍🏼

Updated - since the margin/padding on the multiselect options is fixed px vs. rem like I thought, opted for a px calc factoring in baseFontSize. This can also be adapted in future to just return the element's height value, which we usually pass as an int.