Islam is a great wrestler but he's no Khabib, he's highly technical but he struggles with top control and even in their first fight it was close until Arman gassed.
Charles can pull submissions out of nowhere, that's is speciality. Chris Wade had Islam in a similar position earlier in his career. Arman is not a submission artist, if anything his grappling is more like Khabibs than Islam's is. He's also probably the best GnP guy in the division.
I don't think Islam's wrestling is as good as you make it out to be, he is probably the best in the division but not absurdly better than anyone. He had a hard time with the likes of Arman, Moises and Volk who are probably the only 3 guys with a ground game.
This fight likely ends up being a striking battle. Islam is more technical, makes fewer mistakes, where as Arman is more explosive.