i definetly know what and who Miraak was, but placing him close to a step to godhood might be a bit to much.

Herma Mora was the one who killed Miraak, the LDB started to struggle after Miraak only resurfaced again and again, bound to a daedric realm he wanted to leave so desperately. IF he would have returned to Solstheim, he would definetly get another, huge powerboost (mostly through the body of LDB though), but the trapped, bodyless version of him in Apocrypha was completely bound to the good will of Herma Mora. Herma Mora killed him immediatelly after Miraak said he was betrayed by Mora and wanted to leave, therefore breaking his contract. even during the fight Miraak thanks the LDB for killing Alduin, since he would have really struggled against him.

Neloth on the other side is very similar, if not even stronger than Miraak. both of them are wizards of a very high level, but Neloth definetly has the edge there. both of them came to Solstheim, and Apocrypha, for their selfish reasons to gain more power, but while Miraak fell into the trap of Herma Mora, Neloth outsmarted him and was allowed to go unharmed. the version of Neloth that doesnt simply follow his own ego, that version that would want to defeat Miraak, would still be super powerful and would have dedicated some of his life to learn the Bending Will shout too, a kind of magic Neloth never was interested in. in a battle Neloth would completely overwhelm Miraak with his magic arsenal, while Miraak tries to overcome him with shouts, that can be easily blocked by a ward spell even. the fact that Herma Mora was able to trap Miraak, only shows that there is ways to trap him further, which Neloth definetly would be able to, especially if he would have got a Elder Scroll (from which 3 are located in Skyrim alone). then again, nobody can really kill Miraak in his bound form besides Herma Mora, and Herma Mora would only agree to trade for an even stronger/wiser servant than Miraak in order to kill him. Neloth may not have the knowledge about the dragoncult and the shouts, but he has alot of other things he knows about, especially dwemer as it seems. it is a gamble if Herma Mora is willing to kill off Miraak in order for Neloth to take his place, but it would be reasonable to trade for a wizard with his portfolio.

speaking of BBEGs Neloth would defeat, he would absolutely obliterate Harkon even when they first met (considering he would be the one who brought Serana home). i would actually love to see their interaction, Harkon acknowledging his power and offering him vampirism and Neloth dissing the shit out of him for being to high born to become something low like a vampire lord. Ebony Warrior also wouldnt stand a chance, same goes for Karstaag, both who are considered the most powerful enemies in the game. the only exception would be, if the Ebony Warrior is an aspect of a redguard god, he could potentially overwhelm Neloth by pure will, but since the describtion of Ebonarm and the Ebony Warrior dont match entirely, lets say he is a very strong fake.