we have seen Obito definitely sustains injury when a ninjutsu hits him. When Minatos rasengan hit him, his body was falling apart and he was hurt bad enough to retreat.
And now he tanks kakashi's raikiri like its nothing-
I don't think Obito can hit genjutsu on kakashi who has the same sharingan as him and is skilled against genjutsu.
Therefore, Obito must be invincible in Kamui or the zetsu dna hes using now is better than before.