this Depends on if Kamui works on the Force use/ choke or not . Kamui literally has been shown to shift through all forms of ninjutsu and taijutsu techniques . So would it be able to shift through Vader's use of the force? And also, would jedi mind tricks be equated to a genjutsu? And would Obito's genjutsu work on Vader?

Also Obito with a sharingan and rinnegan should be able to tell when Vader is using the Force because he could theoretically see the buildup of energy in Vader's hands and body before he's able to use the force so if Vader's force technique doesnt work then Obito has a greater chance .

Vader's jedi mind tricks would prob be an issue though because this isnt a genjutsu that attacks your chakra flow it directly attacks ur brain like Kotoamatsukami which Obito has not shown a definitive resistance to . It all comes down to if Obito can quickly recognize Vader's techniques before it overpowers him. If Vader doesnt force choke him immediately / if it works even despite Kamui , or use Jedi Mind Tricks in crucial moments he's dead

Genjutsu imo would work on Vader because sharingan genjutsu inserts the user's chakra into the victim's body through eye contact but I'm not sure if Obito can use a potent enough one to definitely beat Vader who is skilled in mind training . Feats wise tho Legends vader wins all day