About the only reason for playing with a particularly high action is for slide. A *seriously* low action will cause buzzes or rattles if you hit the strings hardish, but it's quite possible (with a properly set-up guitar) to have a fairly low action and not have problems on that score. If you're digging in very hard with a flatpick then a slight raise in action can help, but that's into the realms of fine-tuning for your own playing style, and if you need to ask the question then you're probably not at the point where you need that kind of fine-tuning yet.
As Richard says, lighter strings will give less volume. Although it's also possible for significantly heavier strings to load the top so much that it can no longer resonate properly, causing reduced volume. 12s are usually about the ideal - heavy enough to give a good volume, whilst not too hard on fingers or guitars.
String-wise, I've personally found Elixirs to be a little bit on the dull side. I use Newtones, and I know a lot of other people swear by them too. String choice will always depend on your guitar though. If your guitar is naturally a bit lacking in top-end, brighter strings will help. But put bright strings on something with a complex sound like a Lowden, and you'll just get a mushy undefined "zing" out of it.
But most of all, dynamics will depend on your technique, and on your familiarity with the guitar. With my Lowden, it's like the guitar gets sulky when it's been ignored. ;) If I don't play it for a while, it'll still produce a tune for me, but it's not as clear and responsive as when I've been playing it every day for a week.