I am trying to find out evidence concerning how to handle both timing and ease of modals/dialogs, popovers, popups, alerts and so on. Is there anyone who can share studies or links?
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There is not an exact study which defines this kind of stuff. It all depends on the needs of the design system in place. For example, compare Material Design's modals ( https://material.io/design/motion/understanding-motion.html# ) with the ones from Apple Design System ( https://developer.apple.com/design/human-interface-guidelines/ios/visual-design/animation/ ). You will see that there is not a certain rule they follow.
However, you can find general (extremely general) guidelines, like: https://designmodo.com/design-modal-windows/ , from where you can get some tips of how to make a modal easier for the user to digest.
I hope that this helps you get closer to the answer you are seeking.
You can find some useful information at Material Deign's Dialogs section.