Well, after trying the cheaper (non-certified) adapter that provides a lightning port and a regular 3.5mm jack and finding out that it will only let media audio through and won't work for calls, Siri, or any headphone controls or microphone, I decided to spend more money and get the only adapter that seems like it would actually support everything as it should be--the Belkin one.
Having only briefly tested it out after getting it today it seems like it does what it should: you can charge the phone and have headphones connected that could be used for media playback, calls, Siri, etc., with headphone controls and microphone supported. You still need to use an Apple 3.5mm to lightning adapter if you want to use any non-lighting headphones, but at least it works for all scenarios as far as use of headphones and ability to charge at the same time goes.
We'll see how it holds up over time. It's certainly a bit on the pricier side just to get back the basic functionality that essentially all previous iPhones have offered (realistically Apple should have had one of their own and for like around $20), but I guess that's the way it is, at least so far.