Bryan,

The basic difference between inrunner and outrunner is which part of the motor spins. Inrunner == inside spins. Outrunner == outside spins. Outrunners tend to have higher torque and can spin largish props without the need for a gearbox. Outrunners are much simpler to deal with, making them ideal for newbies to electric. Outrunners don't have gears to strip in a hard landing, making them ideal for newbie pilots. Inrunners tend to be capable of much higher RPMs, so they either spin a smallish prop really really fast, or require a gearbox to turn larger props. Inrunners are more complicated to deal with because of the extra calculation involved in the gearbox. Inrunners have the ultimate efficiency advantage.

Usually, outrunner motors are more than "good enough" for a given application. You don't always need the most efficient setup.

With LiPoly discharge rates, the higher the better. A LiPoly rated for higher discharge tends to give up its charge to the motor more efficiently, applying more power to the motor and/or running longer. Again, usually "good enough" is good enough. You don't necessarily need the best of the best available.

Kv is an RPM/Volt rating used on motors. There's nothing better or worse about a particular Kv. It's simply a description of how the motor behaves. Kv gives you a means to compare otherwise similar motors. The higher the Kv rating, the "hotter" the motor is. That is, the faster it turns on a given voltage. The lower the Kv, the more torque the motor has, and the larger the prop it can turn.

If this is your first plane, I suggest simply looking at what other people are using, and copy their setup. It's much easier to see how things work if you can play with it in your hands.