Today's Rap and R&B. It's the same stuff in every song.
Not true. Experimental R&B is my favorite genre, and I've always been a hip-hop head so I believe I have a good counter-argument to this.
The R&B you're probably thinking about is along the lines of Drake and shit right? He has his own style that's hip-hop and R&B fused into one. Which is why he has ambient sounding tracks that are usually found in newer R&B. I can see how people constantly are getting these two genres mixed up.
This stuff that I'm about to link is more of the progressive/underground R&B that a lot of artists are just barely starting to experiment with.
Notice how the music for these guys is way more ambient, bassy, and soaked in reverb. I mean you COULD rap over this stuff, but then again, you can rap over anything to be honest.
Now as far as content, The Weeknd is really the only artist that has pretty much the same content as a lot of rappers nowadays. Don't confuse the actual R&B artists with rapper-singers.