The good news is that you can do what you are talking about without having to add the Humminbird Ethernet Switch. With the two devices you will have 4 ports to work with and I think this setup will leave you with one open Ethernet Port.

I love my Apex 19 at the helm since I also spend most of my time at the helm. I troll for Stripers and am at the helm unless I'm up reeling in a fish or changing lures. There are major differences with my setup since I'm always trolling. I have my Mega Live attached to the Mega 360 (using a Fishing Specialties mount) and the Mega Live is fixed pointing aft for watching the fish reactions to my trailing lures.

On the Apex 19, I typically have Mega Live on the 50% side and then split the other half with SI and DI. I also have a Solix 12 G3 at the helm and use it for the Chart (on the 30% side) and Mega 360 on the 70% side. I really like that setup as I can keep an eye on everything from the helm... What's coming up as well as the fish reactions to my lures.

Good luck with your setup!