Has Obito shown to use both Kamui and Katon at the same time?
That's what bakufuu ranbu is.
If you're talking about intangibility then no he can't use jutsus while intangible.
If he can't then he still gets put to sleep.
Lol No, obito goes intangible, phases through the ground, & appears at a location where there is no pollen, then he lights it up.
With the sharingan he will be able to react to FTW before it gets out of hand so if he has chomei then he warps on top of it for flight.
Madara's already used Katon on FTW and it didn't work, if anything, it made the jutsu more effective as fire consumes oxygen and that forced the Gokage to inhale oxygen and therefore the pollen.
Scan of madara's katon not working on FTW please. & obito isn't using katon while inside of the jutsu, he will first warp out of the immediate area.
Just because it's bigger doesn't mean it's hotter, so any Katon isn't going to burn Hashirama's Mokuton constructs to the ground, it'd only make Obito's situation worse.
Never said it was hotter, it covers a larger area and fire burns wood so no matter what you try to say a katon of that scale renders
FTW useless. Any other mokuton constructs get either bypassed by kamui or taken down by acid & lava or even bijuudamas.
Hashirama pins down all the Bijuu with Myonjinmon.
Lol not a chance, chomei can fly, & the bijuu can go from their V1-V2-Bijuu modes instantly. Hashi can only place so many gates & with the bijuu changing their sizes at will there's no chance that they're getting caught. Not to mention the entire time he has to deal with the bijuu he will be getting attacked by obito himself who can clean this match up in no time at all with kamui.