Team 1 low diff.
Anyone who thinks that any kage, bar a hokage, can take on multiple other kages, is clearly a fool.
Oonoki has 9 jinton and 4 fodder jutsu max.
If he uses any decent jutsu, the number of jinton he can use is decreased.
Jintons can be dodged, they have a charge time.
MEi's massive suiton are big enough to warrant the use of high level earth jutsu as a jinton won't be quick enough - it wasn't fast enough for muu to jinton a kcm naruto falling from the sky then jumping off sand.
Boil release is enough to get oonoki to stay the **** out of the area - tsunade can keep byakugo on to tank that shit if she needs, or mei can keep the ph low when oonoki's out, and raise it when he's dumb enough to close the gap.
Hidden mist completely shuts off his vision - seeing as mei originates from hidden mist mother ****ing village which usually has mist covering it, i'd confidently claim that she can fight through hidden mist.
tsunade can powerup mei so that heer attaacks dwarf any shit oonoki can muster, even a jinton - if a jinton isn't large enough to cover the enter area, it won't destroy anything beyond it. Plus, jinton disassembles bit by bit quikly, not just everything instantly.
Mei > oonoki high diff.
Mei + tsunade low-mid diff whoever denies this needs jesus.