RE: smith machine or power rack?
they're basically just a frame with adjustable bars for your barbell to rest on - stops it from landing on your neck when you fail. kinda H shaped I guess..
machines are the nice safe way of doing things, and theyre not as effective as free bars because they're in a fixed groove - so your body doesnt have to worry about stabilising it, only pressing, so you dont use as many muscles in the lift..
there are different ways of training chest, db presses, dips, etc, but at the end of the day something is better than nothing and your muscles will still get a workout using a machine (just maybe not as good as with free weight)