Hi there welcome to the forums.
I’m slightly confused by your question so I’m just going to clarify what I think you’re asking and then answer that, if it’s not quite what you were after let me know.
You are getting all actors of class PlayerStart it looks like, and then you are trying to see if any of those have the correct tag, and if so you are wanting to add them to an array of ValidStarts that are valid because they have the right tag? But you are having trouble because they don’t match the exact same class?
If that is the case you can simply change the array you are trying to add them to to match. In this case a PlayerStart object array.
As an aside when you set the class on a GetAllActorsOfClass node the return value will change to be objects of that class, you can always check this by hovering over the return node and it will tell you what it is.
So if you were to change the array of ValidStarts to be PlayerStart object references instead of (I think you said) Player object references, then you would be able to add the ones that are confirmed to have the correct tag to said array.
Hopefully it is as simple as that, let me know if I’ve gone off on my own tangent or something is not quite clear and I’ll be happy to clarify!