Efficient way to make small edits in massive timeline with many vid & audio tracks?

There's a few ways to go about this. FYI movies are often still assembled in REELS of 20 mins (even through there is no physical need to do so anymore) so it's a bit easier to make edits in a shorter sequence. For the actual edits there are a variety of tools and techniques; you can ripple delete or ripple edit and that will move media on ALL targeted tracks, and you can lock certain tracks to keep things from moving. You can also use the GROUP command to keep collections of audio and video together -- say a whole scene -- without needing to nest them. Often what I do when I don't want to mess things up "downstream" is to select everything past the edit point with the track forward tool and move it a good 1-5 minutes down the timeline. then I can make my edits and use the same tool to slide everything back into place. 

I don't know about those "blockbuster" timelines bit I imagine they are the final result of several nested reels put together and un-nested, with minor tweaks to sound design and music. Overall the editing is probably done at that point and no one is going in to make edits in the middle of a 2-hour sequence if they can avoid it!