Superspeck,
I use standard NP1 for caulking-I have used others but that's just what McCoy's had at the time. McCoy's-Bryan, TX is your best bet in the Brazos Valley as this particular McCoy's as far as SmartSide variety. Woodson, Callaway, Pro Build also have some different ones to choose from but the Distributor is in Texas so you really have about 160 skus or different lines of SmartSide so they should be able to get what you need in 2-3 business days.
SmartSide Strand is southern yellopine wafers infused with Zinc Borate, MDI resins and waxes (Termite killer, natural wood decay disrupter-a non toxic, simple salt impregnated into the strand-visine and toothpaste contain it so it's harmless)
SmartSide Fiber (engineered Hardboard to the builder lingo) is maple hardwoods (same formulation as Miratec trim) with the SmartGaurd Zinc Borate Treatment-This product is more available in West Texas and North Texas.
BOTH are covered by the 5/50 warranty.
Keep in mind, these are not "OSB Siding" or Trim craft "masonite". Same comparison with all the Maxiplank Cement vs. James Hardie. One has a 10 year liquid process making from Mexico, the other a more engineered layed cement process. Another example is Advantech Sub Floor vs. Plywood, Old Dogs will tell you "waferwood < plywood", not today. Commodity OSB is superior to CDX or Plywood (APA), while Advantech Rules all and it's Value Added OSB.
SmartSide comes primed like cement and actually only requires one coat of paint and is a non-pourous product. It's a paper paint based overlay that's infused on top and is very hard to chip or break the overlay, if you do, simply caulk it.
Strand is what I use and recommend due to the cedar curbside appeal-easier to work with IMO. Fiber is good too but strand is superior in strength and durability.