Darth Vader (ROTJ) & Luke Skywalker (ROTJ) vs Joruus C'baoth

Force only.
Perfect teamwork.
15 metres apart.

Who wins?

Team

Team. Vader could almost solo, due to C'baoth having zero lightsaber feats (and seemingly not even owning one).

vader solos tbh. he is already to said be either equal to, or stronger than joruus. he also has better training, more experience, likely better powers, more durable, much stronger, and is a better dueslist.

Force only.
Perfect teamwork.
15 metres apart.

Oh, shoot, Force only? C'baoth, easily. Luke has no defense against lightning really, outside of briefly defending against Sidious' lightning. Vader might be able to block the lightning with tutaminus, but I don't think he actually has the TK muscle to defeat C'baoth. C'baoth matched Thrawn Trilogy Luke in a TK struggle over a lightsaber. Thrawn Trilogy Luke>RotJ Luke in the Force, and numerous sources put RotJ Luke=RotJ Vader in the Force. I can't even argue that Vader has superior mastery in the Force than C'baoth, because some of the mad clone's feats of control are pretty impressive. C'baoth takes it in a narrow battle.

Vader is stated to be his equal or superior. The only thing he has over Vader is lightening which won't ki him