I was listening to artists such as RINI, Sabrina Claudio and Bryson Tyler and lthough I can identify that they are very much R&B/Soul artists, I don't know why. I've searched up the characteristics of these two genres but rarely I find distinct characteristics that make up R&B and Soul. Because R&B and Soul music of today is quite different from the R&B and Soul music back then, it's quite hard to put a definition to it.
R&B (rhythm and blues) was a term popularized by the music charts coining as a way of describing Black-oriented radio hits without specifically referencing race. Over the course of the 80 years the term has been in use, it has described many very different types of music. Its primary use has always been the contemporary music popular among black Americans (although the term was in use at one point in Britain to describe music that drew inspiration from American R&B, but was quite divergent from it). The R&B charts have often innovated and anticipated mainstream trends, from jazz, blues and rock to disco.
Soul is a specific type of R&B that became popular starting in the 60s. It was a secular version of Black gospel music, innovated by singers such as Sam Cooke, Ray Charles and Aretha Franklin.
Starting in the 80s, hip-hop became the dominant musical genre in the Black American community, leading R&B to be redefined as the contemporary black music that was NOT hip-hop. In the 90s, that sound was heavily influenced by "neo-soul," a revival of the soul sound, but with modern influences.
Given how listening habits have become more individualized and less racially segregated in the 2000s, modern versions of R&B are distinguished less by who creates them and who listens to them. They are called "R&B" or "Soul" chiefly because you can trace a continuity of influence in them back to the neo-soul stars of the 1990s --singers such as Maxwell and D'Angelo.
As opposed to mainstream pop, modern R&B hits have smoother, more sensual vocals and beats. They are almost always slow ballads, typically on the theme of romance. They tend to have jazzy chord progression and a sound that is simultaneously warm and atmospheric. The instrumentation also tends to be more retro (deliberately reminiscent of the sounds of the past) --a lot of acoustic and electric instruments --as opposed to the technology-forward modern pop sound.
Incidentally, modern mainstream pop also owes quite a bit to 90's R&B, but not so much the smoky neo-soul ballads --it's more like the uptempo hip-hop influenced electro-funk of the times.
Meanwhile, what remains of contemporary black American radio is almost all descended from hip-hop, although that now includes singers such as Frank Ocean, who would once have been considered R&B, but who isn't a close match for what we now think of as the R&B sound.