People argue different ways of how to load footage. Some people like to be very specific about what they are taking off the tape. Personally, I like to load in the entire source, then do my selections in final cut and then use media manager to remove from my drive what I don't need.

Media Manager is a great thing, but a bit of a beast too.

The con of this method would be you need enough disk space to load in the tape to begin with. Probably ends up being a more fragmented disk, but I'm not sure on that one. And you might be inclined to keep more footage on your drive. Pros are - it's much faster to scrub your drive than your tape - and that's the biggest reason I do it. My time is worth more than my drive space.

The the other part of the question.... it's too big to answer briefly here. But one aspect of it is that master clips have properties that when changed will affect all of it's subsidiary clips. Not ALL properties, just some... and sometimes you won't want that relationship. But get the real answer from the manual... I think Volume IV. chapter 4.

Since media manager was brought up in this thread. Just going to comment that I was going to media manage 200 gigs of material and ended up doing some tests which reveled this:

When I had the setting "use existing" (recommended in the manual) - the manage would work as expsected. However, on my drive was only 1 clip from every original captured movie. Yet, FCP would see all of them. I ended up hunting for them and discoering them hidden in a 501>Temporary folder on my drive. I threw out the original movie and the other files did not follow suit.

Solution was to use the setting "move" and then move it to another place. That worked famously.

Read the manual carefully otherwise though. You have to delete original references and such. Requires a little preparation.