That is correct you can play R&B or Neo Soul just using two chords only. Not any two chords, many will work but especially the below.
The first chord is: B flat minor 7th or 9th
The second chord is: G minor 7th or 9th
Try it using alternating four beats each and see how soulful it sounds.
For the chorus you could simply add one more chord e.g. F min 7th or 9th would work well.
There are many R&B songs that are mainly in just two chords, especially some of Erykah Badu’s older albums. It’s all above the melodies you put over it what makes it really stand out.
These chords incidentally sound like they are from two different keys however they do compliment each other especially in this Neo Soul music genre. There are other genres you can get away with playing only two chords for, but you would need a good singer to bring out the melodies to avoid it sounding too dull.
Also check out the video On&on by Erykah Badu, did you know that was just two chords? It’s just Bmin9th and Emin9th, that’ all.