Trees grown in a natural forest grow under more competitive circumstances. There are older trees shading them out so they grow tall before they grow thick and thry grow thick SLOWLY as there just aren't as many nutrients available as in a cultured forest/tree farm.
In a tree farm, trees are spaced to provide good light and to prevent competition. They'll get more of their planted saplings to survive through to harvest. They will also grow to harvestable size faster. The wood growth rings will be wider as well, and the wood will be less dense and a bit weaker.
Wood does not stabilize until it dries. Target dryness is between 7% or so and about 13%. The fastest way to reach this water content is in a kiln. Air dried lumber can take a year or more to dry properly. The proper way to dry lumber in a kiln is to staock it in layers with stickers in between and space between each piece so that drying air can circulate freely, or at least uniformly between pieces of wood.
Kiln drying hardwoods can take 14 to 30 days or longer. A friend of mine owns a yard. They specialize in hardwoods and New England style architectural trim, beadboard, etc. They do not do dimensional construction lumber.
In southern NH, the best lumberyard I know of is Reed's Ferry Lumber yard in Merrimack. When I was building houses, we had to reject very little of the Reed's Ferry lumber.
With most modern construction lumber however, it is fairly important to get it built and sheathed to minimize twisting and warping. If I were to build a structure today that I knew I couldn't get sheathed fast, I would be inclined to get a sprayer set up with Boiled Linseed Oil, or Thompson's Water Seal and quickly spray down the framing to limit moisture movement a bit.
Manufactured lumber is lumber made from oriented strand board and dimensional lumber. Typically an Engineered or manufactured floor joist is an I beam made from 2X4's forming the "flanges" of the I-beam (the top and bottom lines) and oriented Strand Board forming the upright. The glues used to make the strand board are several times stronger than the glue that holds wood fibers together. You don't want to leave the stuff exposed to the weather though or wood rot could cause the strand board to come apart. So If you cannot complete the job within the normal time required to complete a construction project, you NEED to protect those engineered lumber structures and materials. Paint, polyurethane, whatever, will all do the job. If you need to store the materials, place them on stickers to keep them off the ground and cover the materials with a waterproof tarp supported to allow air to move and reduce condensation. Engineered floor joists are MUCH stronger, stiffer and lighter than similar dimensional floor joists.
Engineered lumber is really the hope for the future of building materials. They allow the use of materials that are marginal at best for traditional lumber (including scraps typically left in the forest) to produce superior building materials. It also allows the preservation of older growth forests, because the inferior wood from cultured tree farms is sufficient for the task.
The biggest problem with modern construction is not materials however, it is the lack of craftsmanship in construction. There really is no excuse for walls out of square, plumb and level, improper application of house wrap materials, foundation damp proofing, failure to break off form rods and seal the holes with waterproof coatings, failure to leave sufficient structure when installing electrical and plumbing subsystems, etc. I've seen all of this in "premium" priced housing...which is why I am buying a 200+ year old house. I know it's overbuilt on a timber frame.
You get what you pay for as a general rule. Buy at a discount store and you should expect to get discounted quality.