Which frequency? 2d sonar

[Scesare1]

Okay I'm new to sonars. So don't judge plz. I got a humminbird helix 5 si g2. I got the side and down imaging pretty much figured out. I'm only a little confused with the 2d sonar. I understand chirp and how it works. And the cones and all that good stuff. I'm just a little confused which is best for locating bass and baitfish.? From my understanding it has 3 settings to choose from when picking a frequency. Medium which I assume is 83khz. Then there is high which I assume is 200khz. And lastly there is medium/high which I assume is 83/200khz with the dual beam? Correct me if I'm wrong please. Which is best to use for locating bass and baitfish? Thanks! I only fish tva lakes btw. So no super deep fishing. 40' at the most and that's pushing it 

[WRB]

 83 KHz cover depth for fresh water fishing.

Tom