Mafia 107. Fever and Overdose

Does this mean that this status will be the result after the check? So, the ultimate ability is the same as a normal ability, block + isolation, but it also prevents the target from posting in the thread for a day? The latter will probably be very fun for the target who signed up to play, and then this happens to them.

No, the status remains normal. And even the checkers, if they come to the target of the ultimate ability, will receive the same information as if they had come to a corpse.
This is an ultimate block that goes first and, upon hitting, gives the city a voting advantage. In the late game, this is, in my opinion, a very powerful thing.

So, can the puppet win together with the maniac? Then why would she interfere with him...? Can the puppet communicate with the maniac outside the thread, like the mafia?

No, the puppet is a puppet. She loses if the maniac wins. She cannot communicate with him - she is an innocent victim.

What result does the waifu get, and how does her normal ability work when she loses in the board game?

I am the waifu, and I go to player A. A board game is used on me, and based on its results, I go to player B. I will receive the result from the GM in the form of "Player B's status is such and such."

What happens if the first love uses her ultimate ability on the board game, and then they try to have a game with her? Or if one of the targets of the board game is in isolation?

The first love's ultimate ability is almost last in the list of normal abilities. If the board game players managed to swap her target, then she will use her ultimate ability on another player and receive his status and immunity from him.

If, however, she used her ultimate ability on the board game players, and on the next night they include her in the game, then if the board game players win, the first love will not receive anything, and the normal abilities of the other two players will be swapped. If, however, she loses in the board game, no swap of normal abilities will occur for her and the second losing player.