"will a Low White Piebald breed Low White Piebalds only, or is a Piebald a Piebald with the amount of White being totally non-gene specific?"
So far all true genetic pieds appear to be compatible with each other (as far as I know). It's been said that the amount of white is random and having not produced a single pied myself yet much less enough to look for trends I can't confirm or deny that. There was a rumor on another forum that Peter Kahl was selling off all of his plain belly female het pieds first which makes me wonder if he was planning to keep the ringer bellied ones as breeders for some reason. It was just a rumor and even if it is true there could be any number of other explanations but it got me wondering if the hets that show more of the pied condition might be expected to tend to throw higher white pieds.
"if I invest my money in 100% Hets, then I can breed my own Albinos and Piebalds."
It might take you a while starting with a het pied to a het albino but with some luck you might be able to produce albino pied the next generation. It is always possible, if not particularly likely, that two morphs can't be combined. The two genes might be close together on the same chromosome making it difficult to get more than two copies total between the two genes in the same animal. The combination could be lethal. Or one morph might cover the appearance of the other (not likely in this case but perhaps more likely in something like leucistic and striped).