Q: Ethernet with Airport also on?

Nevermind, I found the answer outside this communities area:

http://www.macworld.com/article/3039842/macs/can-you-use-wi-fi-and-ethernet-on-a -mac-at-the-same-time.html

You can dictate the order of preference for which network source is used in Settings>Network on your Mac. By moving "Ethernet" to the top, your Mac will always use the Ethernet connection over Wifi or any other sources listed below it, so long as Ethernet is an active connection. Should something happen with your Ethernet connection (cable comes loose, perhaps) your Mac defaults to the next source in the list that has an active connection.

Apparently there is no trouble with having both ethernet and wifi connections active at the same time.

Well, since I WANT the ethernet to remain the primary connection, that works for me. If for some reason anyone wants their far more limited bandwidth and slower wifi connection to be their primary internet source despite having a working and active Ethernet cabled source available, then perhaps they have a problem. It can see a reason for wanting the wifi to be active at the same time an ethernet source is active for the reasons I listed in my original post (and a few others), but I am having trouble thinking of any reason why they would then want wifi to be the default internet source over a working ethernet connection. If, for some reason, they want to use wifi instead of ethernet, unplugging the cable seems an easier solution than messing with the network settings. Other than as an internet source and a much faster connection to a network, keeping an ethernet cable connection active has no other functional benefit unlike wifi.