A known wifi network is available.

No, it's off. The only difference is that I'm using Apex Launcher, but there's no setting anywhere that's for wifi.
 
That would be the lovely Wi-Fi popup we all know and love. Should be instructions to get rid of it in the wifi hacks thread. No root required to remove the popup.
 
I've had a notification on my home screen pull down, but this pop up is new.

That's what he just linked you to. That thread has instructions on how to remove both. The second part of the OP's post is how to get rid of the pop up
 
If you have never enabled a wifi connection, you won't get this. But if you log-in to, say your home wifi network, it will start prompting you everytime a big data usage app is opened to use wifi. The fix is easy and painless thru the link above... or just never keep a "known network" saved!