I got another app. I heard it was free and it sounded simple. It’s called Bleach Bypass, and both those claims were true. You pick or take a picture, choose an effect (of just several choices, but you adjust the effect’s intensity), and then you save/share the photo.
The app purports to “add a cinematic quality” to images and saves them at full resolution. I wasn’t really sure what that meant, but I guess it has to do with vignetting, increasing contrast, muting color, and stuff like that. All I know is I like how the edit came out, and it wasn’t forced into a square format. Good enough for me.