darko, 2 songs you want to look at for r&b.
I would include selections from Mayfield, but I don't think there's much info or tabs/chord charts on his stylings.
But a song on Hendrix's Electric Ladyland album has all the voicings and stylings used in old and modern r&b - "Have you ever been...". It's the second song. the hammer on/off voicings, fragments of chords, are classic r&b guitar. Even some of the voicings (chords) found in songs like "Castles Made os Sand" would be good for your arsenal.
The other songs you may want to check out are any of the Isley Brothers stuff.
But just like anything musical, it's not just notes, it's rythym and timing. So play with your eyes (charts/tabs), your ears, and soul.
That's how I learned, I listened to my dad's old cd's/records of these masters.
Ernie Isley, Mayfield, and Hendrix are the holy trinity. Oh! can't forget Eddie Hazel.