Whether a stock will bow excessively is largely predictable before you begin a build. When a blank comes into my shop I square it up right away and then allow it to acclimatize in the shop for six months to a year plus. I will check it every few months to see if it has moved out of square, and if so, how much. If you already know what style of gun you'll make out of a blank you can cut out its profile, square it up, and see how it behaves over time. I have a nice walnut blank in the shop currently that I planned to work into a Fusil de Chasse but I don't believe it is going to lend itself to becoming one due its tendency of twisting along its length. It has been in the shop for two years now and I have squared it twice but it keeps moving, so I know that once that forearm becomes thin it will quite likely develop a major twist. My decision is to either go ahead and attempt a thin Fusil or do something else with the blank. These are the sorts of things you might encounter regardless of the species of wood you are dealing with, it is all part of understanding your specific blank, and wood in general, which comes with experience. When selecting a stock blank it is best to actually handle it, second best is trying to determine its quality from photographs. Heft the blank, does it feel heavy and dense? Look at the end grain, you want the growth rings fairly compact. Note how the figure runs through the wrist, ideally it flows nicely along the wrist but generally speaking it won't which is not necessarily a deal breaker. Eyeball its length, look for signs of cupping or twisting? If possible wet the stock with plain water so you can determine its overall figure. Speak to the seller and try and determine the blanks history since it was harvested. Most sellers have an interest in you becoming a repeat customer so will want to be helpful.
"I am trying to figure out the differences between the major Stock Woods. Specifically Cherry, Walnut and maple."
Good question; The bottom line is that each stock blank is going to have its own "personality." For instance I have encountered walnut that was far denser, harder, than any sugar maple. Two stock blanks of the same species can vary considerably in density, figure and workability. Generally speaking, for recreating american guns of the colonial era you can't go wrong with sugar maple providing it is dense enough to cut well. Red maple is, in my opinion, second, and not to be discounted, because it can work and have figure comparable to sugar maple. In my opinion, again, choosing between walnut and cherry is often a matter of aesthetics, and wanting to use the same species of wood for recreating an old gun you intend to emulate. You can find stock blanks of either species that will lend themselves to being worked reasonably well. Cherry is generally speaking softer than walnut, soft wood resists cutting cleanly and therefore does not lend itself to relief carving very well. Walnut is a fine stock making material, but it tends to have less remarkable figure. One can find solid, fairly easily worked, blanks in both species.
What you encounter, and this holds true for any wood species, but more so with red maple, ash, walnut and cherry, are blanks with both hard and soft areas, dry. splintery wood that resists cutting cleanly, or, often encountered with highly figured woods, wants to break out chunks in the most inconvenient areas. What you want is to choose blanks that appeal to you and show acceptable working qualities regardless of the species.
I hope that helps. Feel free to ask questions.
dave