I hope others chime in with input as I may not explain this correctly, or completely. Receiver outputs are designed to accept those things deisgned to plug into a receiver, ie; servos, electronic switch modules, that will it turn operate those items you have mentioned. You cannot, and I would recommend should not try to run lights, radars, etc, directly from the outputs. Not enough power and the outputs are simply not designed for this type of application.
On my tug, my radars are controlled by slide switches, not connected in any manner to the control system. My lights are set up the same way, except I use a Robbe switch module to turn the spotlights off and on from the transmitter. My horn is controlled by a mini servo that activates a momentary switch.
Please tell us what radio you are using and what functions you want to have. There are several makers of switch modules available, but I use Robbe as they are readily available through Harbor Models. I,m using a Robbe/Futaba F-14 radio with a 12+2 switch module which gives me more than enougn options for my current boat.
2x speed controls for independant motor control
1x speed control for bow thruster
rudder control
air horn
spotlights x2