As far as I understand he will be a good Muslim who follows the Quran and sunnah better than anyone of his time and that's about it. He will lead the ummah near the end times and will fight with Isa (AS) therein. Heres some hadith quotations concerning his attributes, I'm no scholar so don't take this heavily.
>descendant of Muhammad (SAW) through Fatima
>same name as Muhammad (SAW) in some transmissions including father's name
>a birth mark between his shoulder blades similar to that of the seal of prophecy on Muhammad (SAW)
>Large forehead and nose
>will be prepared for rulership in one night
Some hadith quotations relating to his deeds
>will be a pious muslim
>will be given the pledge of allegiance while doing tawaf around kaaba
>an angel will announce him as mahdi
>will take Constantinople
>will fight with romans vs a greater enemy and be betrayed by romans
>will be very just and judge christians by the gospel, jews by the tanakh, and Muslims by Quran.
>Isa (as) will descend from heaven and pray behind him (some hadith transmit it will happen in Palestine during fajr)
Pic related is what the world would be like if Muslims followed in the sunnah of a single ruler and united ummah.