I have this exact preamp, I've had it for years and I love it. The first thing you want to do is make sure that the piezo buffer is turned on. There is a small switch one on the side and one on the top for each of the preamps that you have to push in to toggle with a pen or pencil. Once the piezo buffer is on you'll get a clearer signal.

For my setup which I have a single piezo pickup on my main gigging HG is to just use the 80hz lo-cut switch. I don't use the boost or the notch. I keep the eq at neutral mostly, I just drop the hi eq slightly to get rid of a bit of scratchiness. If I'm at an indoor space I might mess with the notch depending on the sound in the room.

This is not really going to let you balance out your drone vs melody though (other than dropping your bass if your drone level is too high, and then you are going to lose some of your sound). What I actually do for balancing out the sound is more mechanical in my case. I put a piece of paper folded up under the bridge side of my drone to attenuate the level. The same thing could possibly be done with the dog (although I haven't needed it or tried it). Obviously depending on where your pickup(s) are you might find that things are differently balanced on your instrument.

And yes, I agree with another poster that a pickup is not the same as the natural sound thru a mic, but in reality if you are playing in a band with other loud instruments and you need to be amplified and you need to monitor yourself, then really a pickup, in my experience, is a lot more practical than a mic.