What's the best way to manage fps arms, weapons, animations and scope aim?

Hi all,

I’m trying to find a good way to manage my fps arms, weapons, animations and so on.

My goal at the end is to be able to switch weapons, and to aim with the scope at the center of the screen. But I don’t know what would be the best way?

I’m creating the arms in blender. But what is the best? Having 1 skeletal mesh with the arms and the weapon together in order to animate it at once? (like for reloading)
Or having just the arms and adding the weapon in UE?

In addition, how could I manage to have the crosshair (and the scope) in the middle of the screen? Like in COD.

What is the usual best practices in UE regarding fps?

Thank you for your feedbacks.