Topping up '23 Santa Fe 2.5T questions

You can use that Castrol.
The reason why it is SL is that API limited Phosphorus levels dramatically with SM in XW30 grade. However, since that oil is aimed at Euro crowed, it kept strong additive package, therefore staying in SL category. Which is irrelevant considering approvals and intended use.
It is better anything API SP ILSAC GF6.