To check that the motor rotations are correct, I would put the ROV into “manual” mode, set the gain to its lowest setting, put your hand either in front or behind each thruster, then move the joysticks for “forward”, “reverse”, “up” and “down”. Should be pretty obvious which way the thrust should be pushing for those 4 directions.
As for the gamepad mapping, I personally don’t like how Blue Robotics has it set up. I’m used to forward/reverse/turn left/turn right on the right joystick and up/down/strafe left /strafe right on the left joystick. This is more in keeping with other ROVs in the industry. Fortunately, it’s pretty easy to remap everything either in qGround Control or a joystick mapping utility.