Well, to answer about softwoods, used as most soundboards...and to try to be brief, not easy if you're me......here's some basic stuff and a little more.
Metchosin, your "theories" actually are true to some degree and the way the wood is cut is very important to the whole thing, especially when you're talking rarer softwoods like German Spruce. Quite frankly, there is damn little German Spruce at all and its rarely used. Interestingly, we (US) used to send a lot of Engleman overseas and it was RESOLD to us as German....proving Barnum was right. 'Course Bill D. will happily tell you that there is no such thing as "Bolivian Rosewood"...and he's right! But it LOOKS similar and the name is so much nicer!!!! In any case, German, Engleman, and Sitka are the preferred spruces and German is used only occasionally nowadays as the cost is quite prohibitive. Also, since much of it comes from smaller diameter trees runout becomes a problem and very little of it is available for master grade sale. And what's the point of buying INFERIOR German, when Engleman is available. Both are very white and show very little distinct graining from the growth rings. Both are very silky/shiny/polished looking even without finish of any kind. Sitka is stronger than the others and is one of the highest strength woods available....that's strength to weight ratio...and has really nice "give" or elastic qualities and is actually better suited to steel string construction than the others. I also prefer it for Dulcimers (Hammered) if I want to use Spruce, because the instruments tend to retain their tuning better (Strengh to Weight and elasticity is hard to beat). Sitka does not have that same pure whiteness and the graining is far more pronounced. The colors range from off white to a pink-yellow-tan kinda' thing, but I've never believed that had anything to do with the quality, just the aesthetics. Sitka is also without peer for soundboard bracing and tonebars, again owing to the strength to weight ratio. Frankly, once again, in the blindfold test, I'm willing to bet that very few could pick out the spruce being used. But folks, the market is often consumer driven and Engleman is in. I find Sitka to be more attractive myself, but then again, I'm a congenital idiot what got no taste at all!!!
Cedar is used on a lot of Classicals and I like it (as do others) for dulcimers. It takes a different amount and style of bracing as it is not as strong as spruce, but what it does have is an unbelievable stability in a variety of humidities and also, for some reason, sounds better right away as opposed to spruce where age does play a factor. Very pretty too. Redwood is also kinda' neat in that its got that great dimensionable stability like cedar, and if you play HD or other zither things, you know how much fun there is in the constant retuning don'tcha'? Redwood and Cedar have excellent "taptones" and work really well on guitars as well. And BTW, Redwood and Cedar are both very resistant to rot and decay (which would make the unfinished fiddles last without finish....although a thin finish might actually enhance the sound...I'd like to know about that).
Cypress is also being used some but it comes under the "too early to tell" heading. And don't forget that even in guitars, mahogany has been used with excellent results by even the folks at Martin.
Sorry...getting carried away here. Just some random thoughts from your local village doofus.