The RFP does not include an Appendix with taxonomy information. Should we follow the taxonomy in the RCS RFP?

You can use the RCS taxonomy as a guideline, or the old Enhancement taxonomy, which was based on a now-eliminated NSF taxonomy (these are the same document). The important part is that, if there is any question of eligibility or what the discipline is, that the applicants make a convincing case that the proposal has been submitted to the appropriate discipline.