[Brownmoose13]

Prior to my retirement I was in the golf business and was told by management at TM, Mizuno, Srixon, and Bridgestone that between 95%-98% of all amateur golfers never swing the driver the same way twice in a round. Adjustable drivers were and are nothing more than marketing since the OEM's are basically out of what they could change given specs by the USGA. Golfers are keeping their drivers longer and this is what is or has killed TaylorMade as if my information is correct they will announce a sale sometime the 1st quarter of 2017 to an investment group with a certain golfer as the lead name.
As far as shafts there are absolutely no consistent specs between the manufacturers. One company's R flex may spec as Senior with another company and even within the same company a shaft marked "R" may actually have the specs of the same company's stiff or regular. So when you buy off the rack good luck.
How about lofts? Most companies in their fine print will say that the stated loft on a driver may vary +/- 1*. That is why if you google a tour van video you will see that each head is checked and marked such as a head marked 9* may measure as 9.28*. May not make a difference to the everyday player but it does to a tour pro.