Absolutely no idea (yet) itΓÇÖs too new of a platform to give any real indication,
what I CAN say is when IGTV game into play, a vertical format, Gary Vee kept producing in landscape, because ΓÇ£if you canΓÇÖt rotate your own phone, how lazy can you be?ΓÇ¥ I mean if youΓÇÖre on mobile watching YouTube in full screen, youΓÇÖre going to be rotating it anyway so itΓÇÖs not that big of a deal.
I donΓÇÖt think weΓÇÖre going to know much until next month or even next year. No doubt TubeBuddy is already looking into it from a study and education standpoint. More whoΓÇÖve used it can probably share their experiences.