Victor wooten has incredibly low action, when I played some of his basses, I was amazed at how they virtually played themselves in a sense.
he plays with a very light touch most of the time, and he is ALWAYS relaxed, but he knows how to dig in if necessary.
Speak softly and carry a big stick and all that

it's okay to let your amp do most of the work in letting your sound out.
another thing about playing fast, just food for thought, playing closer to the bridge the strings are tighter and it's easier to brush on them and get a stronger sound, and they also don't bend as much making it easier for you to alternate very fast, now, ultimately I can play just as fast on top of the neck as I can on top of the bridge, but it's a little easier to do it near the bridge, and requires less work.
just food for thought, bridge playing also changes your tone a lot, so you'll probably want to work with what you like.