I guess we'll disagree on Jacare and Lovato being the best bjj practitioners of all the but they are among the absolute elite.
My concern with Mousasi is that he is a bit past his prime. Five years ago, Vanderford would be out of his depth but now is different. Even an unathletic, although very good wrestler, like John Salter, was able to control Mousasi in the ground for the better part of 2 rounds. Vanderford is a younger better version of Salter, so I have no doubt in my mind that he will be able to take down Mousasi. How much damage can he inflict on Mousasi is a different story. Im almost positive he cannot finish Mousasi, but he very well can dominate him on the ground.
The other concern is that Mousasi seems to be underestimating Vanderford's ground game. He suggested that if he gets taken down, he will just stand back up without being too worried about damage or subs. If Mousasi doesnt take Vanderford's ground game serious he will be in for a long night.