Your question about the "W" is a good one, and I don't know for sure. It's like the "S" in API SJ and the "C" in API CH-4 engine oil performance categories. Everyone thinks the "S" means "spark" and the "C" means "compression" for gas and diesel engine oils. But actually the "S" came from "service" meaning service station, because that's where gasoline engine passenger cars used to go for an oil change. The "C" meant "commercial" because trucks were diesels and would go to a fleet or business facility for an oil change. Fun history stuff.
The sponsored race team started with off-the-shelf product because of the advertising campaign - you can buy what the team races with. This was up until only a few years ago, which proved that race oils didn't automatically have to be exceptionally special to run well.
Probably because of smart folks like you, it grew into a performance disadvantage, so special formulations were developed for them. Being conservative, we didn't make huge step changes, and we've developed an oil that has the low friction, good antiwear, and proper viscosity requirements needed for the valvetrain parts. Not knowing all the engine rules, I assume that cam lift rates with the required small diameter lifters are probably the area that keeps builders up at night; the good cam profiles are also the ones that come closest to hitting the edge of the lifter rather than coming up underneath it. And to provide low friction with good antiwear is an additive balancing game - both additive types compete for metal surfaces, but too much of one means the other won't be around to do it's job.
As for viscosity, a lot depends on cooling the oil and quantity of oil. The car has a large oil reserve, and they can pretty much control the oil temperature to whatever they want. They like small holes in the front air dam for aerodynamics, so running a thick oil with less cooling (a little hot) is not bad thing. Running a thinner oil a little cool is the same thing as far as the engine is concerned -it sees both as the same viscosity. Nothing we've done so far is improved by using a synthetic over a good quality mineral oil. Additives provide anti-wear, reduce friction, oxidation control... there's no critical feature that is further enhanced with the use of a synthetic. Sure we use a really good quality mineral oil because we don't want to develop an oil that isn't robust overall, but from what we've learned engines need, it's the additive formulation that's critical.
Drag oils are likely synthetic because they are so very thin. A mineral oil at that low visocity would tend to be too volatile.
Enough hints - after this, you're on your own!
