For my web mini-series I plan to do it all as png series, like Animagic, but export at 1920x1080, assemble in DaVinci Resolve and scale it up to 4k there for export. That's waaay faster than trying to render it in 4k for me, in my tests, but you have to have DaVinci Studio (actually why I forked out for the Studio version) to do it.
So some of it might depend on what video editor you're using--I don't use Premiere Pro anymore, for example, but I'd imagine new versions could do that, too. I do all tests renders as MP4 or MOV, and haven't actually posted anything with the above process, because so far, everything is a test
Everything I have on YouTube so far went up as 1920x1080 MP4 or .MOV. It's tolerable quality but not fantastic.
If you happen to be a Resolve Studio user, I posted this video a while back on exact settings that get you 4k with very little quality loss on YouTube: https://forum.reallusion.com/481565/Helpful-Export-Settings-for-DaVinci-Resolve-17-Studio-Users-for-Getting-Good-4k-on-YouTube
Another huge benefit of the png series is being able render transparent backgrounds for compositing, BTW. Which I'm starting to need to do with big scenes. And doing that, but like DataJuggler in 4k, might be just the perfect midpoint for what you're doing.
Lastly, I'm buying several external drives, and they will be (sigh) velcro'd to my beautiful new laptop's monitor as soon as I can bring myself to do it, because I filled two terabytes with just assets and scene files, not final anything, as soon as I installed everything. I might be a bit of a digital hoarder, ahem. But yeah, animation and disk space are an inverse ratio.
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