Actually the original NAC was not R&B heavy, That was Quiet Storm. NAC played R&B but also more of the pop/rock sounding stuff like Everything But the Girl, Kevyn Lettau, Julia Fordham, Leslie Lettven, Michael Franks, Basia, Full Swing, Nicky Holland etc and a lot more guitar based stuff that was not Benson-influenced like Ripps and Acoustic Alchemy, Pat Metheny and even some flamenco/world like Strunz and Farah and Ottmar Liebert. There was R&B in the mix but it was not exclusively R&B and it was also not nostalgia driven. The content was largely within a 10 year period.
San Francisco had stations in both approaches: KBLX (?) was Quiet Storm and KKSF was NAC. Several other markets had both also, either fulltime or as specialty segments.