I don't know anything about Reiji besides what I read on here but he would stomp the Naruto-verse. If he is planet level then the only being that can match him Dc/potency wise is Kaguya. However Kaguya is only massively hypersonic+(mach 4000+ exactly) and Reiji is LS or FTL. Also Kaguya's planet busting attack takes time to charge up and she can only use it once at full power before exhausting all her chakra. From what I read about about Reiji his planet busting attack can be used multiple times and thus would be greater than Kaguya's and even if Kaguya's planet busting attack is stronger than Reiji it won't matter because a massively hypersonic+ Kaguya isn't going to lay one attack no matter what on a LS or FTL Reiji.
AGAIN, "Kaguya and Reiji are equal in terms of DC, but while Reiji is faster than her, she has dimension hopping, portal opening, and has reacted to characters faster than Reiji.".
Does no one remember that Madara caught Minato out of his warp, and ripped his arm off while he was teleporting away? MINATO WARPS AT LIGHT SPEED. Madara was nothing compared to Kaguya, stated.
They would fight evenly in terms of DC, but when Reiji tried to get close with his speed, she would easily grab him, and fling him into a dimension with a planet busting biju ball. He can't stop it from blowing up the dimension, so he dies.
Well, if he runs out of mana, then he's screwed. Thing is, Kaguya isn't much of an actual fighter considering how fast she burning through her chakra against Naruto and Sasuke. And considering she had the chakra of virtually every being on the planet added to her own along with the juubi's, that's really saying something.