So I was wondering how to make a character aim in an fps mode cause other tutorials in YouTube mostly uses tps mode and also is it as simple as making 2 cameras and switch them when needed? And also what does aim offset do?
anim offset: https://docs.unrealengine/latest/INT/Engine/Animation/AimOffset/index.html
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The key concept behind Aim Offsets is that they are designed to be additively blended to existing animation. Therefore, if you were using an Aim Offset to make a character aim a weapon, for example, you would want to make sure that the other motions on the character are not getting in the way of that additive motion. Put another way, your run, idle, jump, and so on should have relatively rigid arms so that they can be additively controlled by the Aim Offset. **
scope zoom: ?v=U88LWbVv9BY (there he also shows how to zoom) 
Thanks for the explanation but for the zooming part you got it wrong what I meant by aiming is that aiming ironsight aiming like the one in bf and cod
Ah ok, now I know what you want
The easiest way would be to to just create special ironsight animations for your character -> then when the animation gets played, the mesh will be moved with the animation to the right position
can you just use another camera and switch them only when needed and smooth it with vinterp to? cause this sounds simpler and it works really well in unity
That would also work, but I recommend you to still use at least 1 ironsight animation to get a more realistic effect
Here is how you can switch the camera -> https://answers.unrealengine/questions/45130/switching-between-multiple-characters-within-the-c.html