I am using Tinker Board with PiCamera v2.1. How do I set the Color format for the captured image and also how to set exposure params?

Question

I am able to capture NV12 format pictures using Tinker Board with PiCam. I am using gstreamer pipeline with v4l2src plugin to capture images as follows:

gst-launch-1.0 v4l2src ! video/x-raw,format=NV12,width=1640,height=1232, framerate=20/1 ! jpegenc ! multifilesink location=./images/image_%02d.jpg

I have tried using all the formats that are specified using "gst-inspect-1.0 v4l2src" but none of those formats give me an RGB image as output. Please help me out on how to capture an RGB image! Also I am unable to manually specify the exposure time for my Picam while capturing images.Any suggestions on how to do this will also be very helpful??