A simple loop antenna should not be earthed or grounded and using a non-metallic pole will avoid distortion of the antenna pattern.
You are correct with your installation of the Wellbrook and a simple loop antenna with the Loop Antenna Amplifier +.
The cardioid loop was an example of a different type of loop antenna based on an original design of C and S Antennas back in 1974. This adds a resistor at the top of the loop and grounds one side of the loop to give a cardioid pattern with low angle properties. Another advantage of the cardioid loop is that the antenna element is earthed or grounded so it will help with lightning protection on exposed sites.
By the way it's good to hear that the Loop Antenna Amplifier + is working well for you.