Collision capsule of the player shouldnt be responsive to visibility anyway.
Use the defaults.
Player Mesh shouldnt have any collision unless you are doing something special with physical movement component.
Gun blueprint mesh cannot have any collision.
Or it will interact with character capsule when you equip it.
When you drop a gun you acrually just drop a static mesh copy of it.
The collision on that should likely be the same as the character capsule.
And yes, that does mean that the character capsule would “hit” it.
Thats fine. Normally you do other things like pick up and equip ammo/the weapon, so you need that interaction.
Simply create a proper mesh model of the gun to drop, and give it a collision hull that makes sense.
Otherwise, for more complex interactions, you use collision channels and set things up however you need.