RE: Looking for an EP plane for the back yard/ park.
You're going to need a pretty large back yard for a Zagi. Mine used to be able to cross a 15-acre field pretty quickly. The noise might also be an issue if you have neighbors. Parks have across-the-board banned flying due to the noise the Zagi makes. Frankly, some people are too sensitive... You can make all the noise you want, yell and scream bloody murder and kick each other in the head on the soccer field, and that's ok.
Anyway, I wanted to address the onboard gear. Right off, any new servo you buy, be it Futaba, JR, Airtronics, Hitec, GWS, FMA, etc. will be plug-in compatible. There are two types of receivers, "JR/Airtronics" and "Futaba/Hitec." Hitec, GWS, and FMA make receivers of both types; make sure you get the right one. An okay park flyer receiver is the GWS R4P, but it's a little glitchy in a busy environment. A better receiver is the FMA M5. Servo choice will depend on the plane, but most small park fliers use the GWS Pico servo.