Hi.

  My use of multicam has been somewhat "rare", and then only in VPX.  (Your mention of pressing 1 on the keyboard has actually taught me something new!)   However, what you need to remember is that, having selected the "view" from one of the cameras, MEP/VPX will stay with that camera until you select the other.  IOW, you can use the mouse and timeline indicator to "scrub" through the footage (by dragging that indicator at its triangular "head"), simply choosing the exact point at which a camera change is wanted and then clicking on the image from that camera.  

 Personally, I prefer to work through all the footage and make the camera changes in "real time"; it's amazing how often "mistakes" that were previously unnoticed suddenly become very obvious!   

As to your last question, re the video on tracks 3 and 4, IMO it's entirely up to you!  It will not be rendered to your final output; only the contents of tracks 1 and 2 achieve that status.  Your original footage (the content of tracks 3 and 4) always remains unchanged on your hard disc; MEP is a non-linear editor which means, amongst other things, the original footage, even when "edited", is untouched.  MEP creates an EDL (Edit Decision List) which is an internal "data" file which tells the render engine exactly what to take from which section of footage, what transitions/effects etc to apply to achieve the finished product.   

So, for me, I tend to leave those original tracks in place in the saved project; for one thing if further editing is required it could be a real pain to have to set-up the fully-aligned tracks again!   One other thing occurs to me: you mention you leave tracks 1 and 2 empty for the "edited" footage (which suggests you have your audio on a separate track, as I do) but your "raw" video on tracks 3 and 4, so no separate audio track.  I wasn't aware you could "mix" the track settings like that, or is this something else I've learned new?  

 Jeff