@Roy_Wierer.Seda145 is right. You don’t need to worry about casting unless it affects your performance. But using interfaces is a good practice.
Since you want to get multiple references and variable I would go with Interfaces. This way you would have the groundwork to use this references in other classes too. How you structure them is totally up to you. Choose whatever suits your needs.
Another way (But I don’t recommend it) would be casting the references at the beginning of the game and storing them in variables. I beleive you can see what is problematic with this approach.