If the game doesn’t exist yet then you are thinking way too far ahead.
For any given attribute, somehow that value has to make it into the correct spot in your game before it can be useful.
Numbers by themselves are utterly meaningless.
Make the game enough that you CAN have splash damage, then expose the splash damage parameter as some kind of attribute.
Until then all the stuff people type here is going to just be meaningless noise.
In Unity, ScriptableObjects are generally used for this sort of configuration stuff. Here’s some more reading:
ScriptableObject usage in RPGs:
Usage as a shared common data container: