Basic FPS hand setup with multiple animated weapons

Hi,

I'm having a bit of a trouble for a few days now trying to understand how the workflow is between animating arms/guns in Blender and exporting the right for Unity.
My goal is to have a rig for multiple weapon animations / differnt guns.
I watched a lot of tutorials on YouTube, but they always describe how one gun is animated with arms. T$$anonymous$$s then gets exported to Unity with all the meshes for the arms and the (one) gun in it.
As far as I know t$$anonymous$$s isn't optimal.
I t$$anonymous$$nk i need one arm rig and just place the correct weapon in them and play the right animations for it.
W$$anonymous$$ch brings me to my troubles...
I dont't understand how I can animate the rig in Blender and transport t$$anonymous$$s to Unity so that I can build up my FPS $$anonymous$$erarchy.
Do I export the meshes for the guns in the same file with the animations?
Do I put the gun bones in the same armature as the arms or do they have a different armature?

Right now my setup looks like t$$anonymous$$s:

And my $$anonymous$$erarchy like t$$anonymous$$s:

I would now add more bones under the "gun" bone for different weapons and animate them.
But how do I continue from t$$anonymous$$s when I dont't export all the meshes wit$$anonymous$$n the export to unity?