Just buy (2) "2F to 1M RCA splitter" (google it). You don't NEED a switch. A switch is nice if you want to be able to not have to turn the sound down on the TV when you want to listen to the Air Play.
As to sound quality, unless your have system that you have cost you 2K$ or more and you have a listening environment to support it, you probably cannot tell the difference from 4$ connectors and 40$ connectors. Possibly on really bad ones you could tell, but unlikely you would get connectors that bad. Connectors that bad aren't cheap, there defective.
The mixers allow you to adjust the volume of each input relative to each other while they are being played at the same time. You don't NEED that either unless you want it.