I think regarding experiments you can do easy ones or of they are larger promise to add them to the camera-ready version (if you think it is feasible). Regarding notation you could just clarify questions in the response form, right? This might hep for formatting, as it mentions that superscript/subscript is possible: https://academia.stackexchange.com/questions/165872/start-v2-softconf-what-markup-is-allowed-in-reviews