I believe the Acolytes of the Beyond was created so that a new Sith Lord could be identified. I think this new order may have something in common with The Brotherhood of Darkness from Legends where these new Sith Lords didn't use the Darth Titles--being known as Knights.
I'm not sure where the Ren name comes into play, but the word Ren has some interesting meanings. In Chinese Ren is a confucian ideal to describe the good feelings a virtuous person experiences when being altruistic. In Japanese Ren can mean lotus, like a lotus blossom, a symbol for enlightenment, and also love. In Egyptian, Ren, is the name given to a person at birth, and it is also part of a person's soul.
So it would be interesting to look at the Knights of Ren as people among the Acolytes of the Beyond who are found to be Force sensitives. Their force sensitivity allows them a stronger or deeper connection to the dark side of the Force which could be seen as a form of enlightenment.
Now this would not make them Sith as in the Sith from Darth Bane that we saw in the Prequels and the original Saga, but like the First Order was born from the ashes of the Empire, the Knights of Ren, and the Acolytes of the Beyond could be born from the ashes of the Sith Order.
It would be even more interesting to think of Kylo Ren as being this person who is born from the ashes of Vader who rises through the ranks to assume control of both the Knights of Ren and the First Order--both these things that Anakin destroyed when he turned back to the light are now being led by his progeny.
Now right now--everything I'm saying is complete speculation, so don't go running crazy with this information.