Athletics is used for
-Making and resisting Shoves
-Making and resisting Grapples
-in general can be used for difficult climbing, swimming, jumping, etc.
Acrobatics is used for
-Resisting Shoves and Grapples
-not falling on icy surfaces etc
-doing nimble stuff, which probably won't be included that much in BG3 because that would require specific coding
In summary, Athletics and Acrobatics should be used for Shoves and Grapples. I'm not sure if shoves in BG3 use Athletics since their formula doesn't appear in the combat log.
They're also used for general checks, like breaking down a doorl, etc that might come up in various cutscenes/events
