In series -
1) Well, the reason to use the OEM-fit is so that it fits like the original filter. So it's a lot easier than redoing the current plumbing - just unlatch the air filter cover, lift it, pull out the paper one, install the clean and oiled K&N filter, and relatch the cover.
2) Dunno.
3) A supercharger is driven off the motor directly, by means of a belt (or chain for some designs), just like the alternator etc. A turbocharger is driven by the pressure of the exhaust gasses - they spin one side of a turbine, the other side sucks air in and pushes it into the intake.
There are advantages and disadvantages to both.
RwP