I've figure it out, and have it working now. Very simple modifications to arduino code without touching PID algorithm. In PIDTASK I've added a variable speed to each wheel at bala.SetSpeed based on Joystick input received through espnow.
I will like to control Bala2 with a joystick. I've done remote control with CStick and Espnow for 4 wheels, but will be of help some advice on where to modify Bala2 wheels speed for this purpose. Any existing code will be great. Thanks.