The underlying height and setback provisions shall be modified as follows:

In Residence and Commercial Districts, all buildings shall follow the applicable height and setback regulations for residences set forth in Section 23-43 (Height and Setback Requirements in R6 Through R12 Districts), inclusive, in accordance with the applicable residential equivalent, except that in C6 Districts without a letter suffix, the height and setback provisions of paragraph (b) of Section 123-652 (Special base and building heights) may be applied for the applicable residential equivalent in lieu of the provisions of Section 23-434 (Height and setback modifications for eligible sites).