yep getting clear now...
Shoudn´t be a problem with 2 layers and the clips in the same collom..
You can animate the opacity of each file and with the envelope it can do all fanzy stuff you need to.
with click the collom you start both clips. inside the two clips you can animate the opacity (timeline & envelope and plamode "play once")
now you can set all as you like..fade in / hold / fade out all like you need it.
(if you have a transition mode (effect) that looks like your "beam in" clip that you can spare the beam effect layer but that can work or not... with the top solution you are safe)
For the BG you take another layer on top of everything and chose the layer to ignore colom trigger so its not effected by the start of the other stuff