How to test 4 wheel motors on a Rover

Hello to all.

New to ardupilot and mission planner, but slowly learning through this great forum and reading the documentation.

A run down of my hardware:
SiYi MK15 radio system
SiK telemtry radios between laptop and AP
Cube Orange
2 x Drotek Sirius Rover GPS for Moving Base/Yaw configuration
1 x Drotek Sirius Base GPS for RTK
4 x motors which are controlled by 2 x Dual Motor Controllers.

I have been testing and setting up the autopilot with gps and so far everything seems ok.
Today I was trying to test the motors for the first time.

Before I mention the tests through Mission Planner, motors have been running fine and was tested with SiYi MK15.
MK15 was connected directly to the dual motor controllers via 4 PPM channels.
PPM1 is set for Forward/Reverse
PPM2 is set for Motor Difference(yaw)
PPM3 is set for Motors Enable
PPM4 is set for the 3 different speed levels.

Was able to manually control the rover through the standard RC channels.

Now, I have no clue how to proceed with removing the 4 channels rc outs from siyi and connectingbto Cube Orange.

Siyi SBUS connected to Cube RCIn.
Radio been calibrated in Mission Planner.

For some reason, when I first power all hardware and connect MP to AP, it shows up as Armed. Unable to force a Disarm.

Servo1 is set as Steering Left and Servo3 is set as Steering Right.
Also tried setting RCpassthrough for servo6 and servo10(these are the original channels used for Motor Enable and Speed levels).

Feel very lost and dont know how to continue.

Your guidance will be greatly appreciated!