I use the FaceTime camera on my 5S once a day for 10-15 min for video chat. It's not pretty. It's choppy and blurry. Selfies are also not HD.
The camera "works" but the pictures/video ain't pretty.
Nobody cares on the other end about your camera. And FaceTime does not even support 720p. I got SE after using 5s for 2.5 years. And I must say that even rear camera hasn't dramatically changed over these years. Comparing side-by-side photos and videos, taken from these devices, there is not much of a difference. If you start to zoom-in photos, taken on SE, you'll notice noise all over the picture well before you start to see pixelization. Same thing with video. 60fps is noticeable, but 4k is just waste of space and marketing. Quality of video is pretty much the same, comparing to 5s. Just better stabilization and faster focus.
At the end of the day, I doubt that you'll be watching your videos and photos on a big high-res display, like Retina 5k, trying to see every pixel of your picture. Most likely you'll be posting your selfies to Instagram or Facebook, which will compress them down to ~1Mb size. So it's all up to you.