How can i have a smooth transition between the first person camera and the third person camera ?
yes but no. i want a transition that smoothly goes one into the other
Couple of examples:
It did what i wanted but also added a couple of bugs
Sounds like a truly legitimate development process. 
Thanks for the vid link. It helped me see another way to do this.
But isnt he wrong at t=38?
He is 1) moving the Camera location (distance), instead of 2) changing the distance on the Camera boom.
I heard/read somewhere that a wall glitch happens if you do #1 - if you get too close to a wall, the Camera/boom glitches and [the wall blocks view or turns invisible - map exploit (I forgot which is the error)], instead of the camera boom moving in a little to correct the view.
Did you see this vid (which was linked at the first one)?
This has the GLIDE between the 2 cameras.
Also you asked how to change Character cameras (cameras that are inside the Character BP). But if you need, there is another Node that changes (blends/glides) from Character camera to a Camera in the world.