All techniques allowed. However if Izanami is too hax then it'll be taken out. The Second is his his actual body, not his ET body. Itachi is healthy for once. Fight takes place in the current setting of the manga.
"To all visitors from Transylvania looking for the head of Voivode Dracula: Yes, we have it. Yes, he's dead. No, you cannot see it. No, he will not return and invade you again. It has been over thirty years, please stop pestering us."
Yeah right now everything favors Itachi. Tobirama's FTG isn't as good(he never uses it for ranged attacks like Minato's kunai), his Edo Tensei isn't usable, and his clones aren't particularly impressive even next to Itachi's.
Itachi. He's got the sharingan, the rep and on-screen/panel feats. Tobirama will make it a fight because of his intelligence, but he needs beastly on-panel feats to contend with Itachi.
But if Tobirama is allowed the Edo Tensei then I can't see why Itachi would be denied Izanami. And even if Tobirama could use it the only people we know that he also knows to be dead are either stronger than him or vastly too weak to help him.
"To all visitors from Transylvania looking for the head of Voivode Dracula: Yes, we have it. Yes, he's dead. No, you cannot see it. No, he will not return and invade you again. It has been over thirty years, please stop pestering us."
Tobirama's FTG is less than Minato's, and since there are several posters who believe Itachi wrecks Minato, then Tobirama is definitely screwed. Without ET, Tobirama has no chance of keeping up with Itachi's techs.
Only the Tobirama we thought we were seeing was actually an Edo Tensei of Tobirama's brother, who regenerates and proceeds to lay his wood across Itachi's forehead.