Can I set variables for other scripts?

ScriptA:
public GameObject Player1;
public Player player;

void Start(){
Player1 = GameObject.FindWithTag("Player1");
player = Player1.GetComponent<Player>();

ScriptB.player = player;
}

ScriptB:
public Player player;

 

I honestly have no idea what you're asking. Yes, any public instance variable can be set from another script given you have a reference to an instance of that other script. You should be able to set player in ScriptB from ScriptA.

 

Yes you can, but you need a reference to Script B.

For example:
GameObject.FindWithTag("GameObjectWhereScriptBIsAttached").GetComponent<ScriptB>().player = player;

 

What @Varhius said. Additionally, here's a handy list of ways you can get references to other objects!