Ultimately, all the choices you make as far as electronic equipment are based on the specific airplane. However, it's not as integrated as you believe.

There are actually two separate, yet equally important, electronic subsystems on an electric airplane. These are propulsion (battery, motor, and ESC), and control (receivers and servos). For the most part, these can be addressed as completely separate entities; you would have to try extremely hard, and use some very strange gear, to make these two subsystems incompatible. ESCs use the same control signals as servos, and all servos use the same control signals, so you can attach virtually any available servo to any available receiver, and it will work.

The control subsystem is fairly simple to "spec out." Unless you designed the airplane yourself, and have no clue about equipment (a highly unlikely combination of circumstances), the airplane will come with recommendations for a particular class of servos and receiver. All the major brands (Hitec, Futaba, JR, Airtronics) have receivers and servos for practically any size airplane, and there are some highly-recommended third-party brands as well (GWS, especially for smaller park flyer stuff).

Propulsion is a little more involved, but if you don't want to get into the real technical aspects of figuring it all out from scratch, virtually every size and type of airplane has been electrified, and posted about in one forum or another. If you can't find a plane similar enough to the one you want to electrify that you couldn't simply copy the power system, you aren't looking hard enough.

In a nutshell, the power system starts with the estimated final weight of the plane, and how you intend to fly it. You use this information to figure out how many Watts of power will be necessary to fly the plane like that, then you use the Watts to come up with a reasonable target value for Volts and Amps. With that information, you can then choose both the motor and ESC. Of course, that's a high-level view of the process.