Building optimal RC flying wing
You don't need an optimal design to have fun.  General guidelines:  Your model should weigh around 500 - 700 grams.  Wing span around 1.5 meters.  Chord around 0.2 meters.  But you really need to nail down your speed envelope.  Too fast will be difficult to control, too slow and it's an indoor delight but an outdoor nightmare (due to wind).

A good place to start would be a chunky reliable design similar to a Piper Cub or Cessna 152.  Shorter more highly loaded wings should help you find the sweet spot of around 7 to 25 mph, which is good for R/C planes.

Build an engine/battery/servo frame that can easily change out wings and empennage as you fine tune your design with gliding and powered flights.

You may wish to start with a slightly cambered KFm 1.  Slower speed and lower wing loading should give more endurance, but will be blown around by the wind and will actually be less efficient distance wise into the wind.  Go conservative on your first build.

Control surface dimensions can be had from foamies at your local hobby shop or R/C club, and more information is available at the RC Groups website.