I have 1x FS 6c Tx with matching 6c Rx`s. 3x BEC`s, 2x 4500 LiPo batts.
Lipos only if you really really need to keep the weight down.
3xBEC. ??? 1 ESC per motor (2) if you need independent control. If they both have a BEC fitted, disable one by disconnecting the centre (usually red) wire of one. 1 servo for the rudder. Stick with brushed motors for a simple life, probably something big and slow running with a lot of poles and gear them down using a pulley drive for quietness, a gearbox if you don't mind the noise, maybe a worm drive if you can find the parts.