imo
The jr ds821 would be good for all your control surfaces and the throtle too, from what i can gather this is a 40 size plane so, the torq on these are plenty for this plane, for 3d it is pretty much a necesity to have hi speed servos.
The best way to get the cg set is to do some flight testing, take it up, pull verticle at 45 degree angle and roll inverted and let go of the sticks, if it starts to nose down then it is nose heavy,
if it climbs then it is tail heavy. The way my planes are set up is so that they are perfectly balenced.

hope this helps