Around the level of Juubi Jin Obito.
The weakest of them all.
The underestimation of Nagato is real.
He'd be definitely be stronger than Juubito because of Nagato's mastery of Rinnegan. Obito didn't even use the rinnegan when he was the Jin, neither Kamui. Nagato is easily above him.
People think Obito is tough shit even without Kamui Lol. A jinchuriki Nagato would easily be stronger than JuubitoThats what im saying. Obito couldn't even make full use of that form, because he couldn't full use the rinnegan. Plus his kamui is a non factor since he cant use the phasing.
Juubi Jin nagato all fan hype aside would take sasuke and Naruto on one on one. Implying this is the original red head nagato. He would be far above juubito level since unlike obito he can handle two rinnegan however he would be below juubidara level. On a power scaling he isn't in the top five, he'll be in the top ten though. Juubi Jin nagato however ability wise may be more devastating than juubidara just not power wise. Asura path with juubi enhanced power would be formidable. Any of the paths that are juubi enhanced are devastating. Juubi Jin nagato would be strong enough to hold his own against Naruto and sasuke. They may be able to still beat him, Naruto with ease due to the TB rasenshuriken elements. I'm not sure what saauke would do.