Hey @AllGamesSuck!
As far as I know, and I may be wrong on this but as far as I know…
Anything that is guaranteed to exist does not impact performance when cast to because it doesn’t need to be loaded, it’s always there. The player (if there’s only one kind of player), the Game State, Game Instance, and Game Mode should all be fine to cast to with no performance hit.
In other words, for these things, casting to it once and setting it might be easier and more convenient on your graph. Either guarantee a way to SET it every time it changes, OR cast every time. This is NOT good advice most of the time.
Hope that helps!