Here's how my Herbie looks:
I like to have a trickle down the emergency drain. I find that there's a wider "sweet spot" like this. There's no additional sound since the surface tension of the salt water makes the bit of water going down the emergency drain stick to the walls of the PVC eliminating any dripping, gurgling or splashing.
I've completely shut down the main drain with the ball valve and the emergency drain handles it without issue. Once the amount of water exceeds a certain level in the emergency drain then I start hearing the telltale gurgling and splashing.