There's no way I'd have watched both films on the same day. I knew I'd need to lie down in a darkened room after seeing Oppenheimer to recover (so to speak), so seeing Barbie instead directly afterwards would have been intolerable. As Stuart Heritage says in this article in The Guardian, for the good of your nervous system, don't watch both in the same day. :)

https://www.theguardian.com/film/2023/jul/22/barbie-oppenheimer-double-feature