Change video cam resolution iPhone 4S

Hi everyone,

I still use an old iPhone 4S with iOS 8.0. I don't want to replace it or to update it, I would just like to find a way to make the video resolution smaller to save space. The camera records by default in 1080p and I would like to change it to 720p. There are some apps that allow this, I tried some of them, but I had various problems with them.

Top Camera - the trial version of this app allows recording videos in 640x480, so I thought about buying it to unlock all the other resolutions, however, I noticed that the focus doesn't work so well in comparison to the default Camera app. It is kinda slow to focus. I'm not an expert, this is just my impression.

ProMovie - it offers what I need, however it works badly on my phone. Either the phone is too old and slow or iOS version or maybe the app is buggy. Some of the buttons fail to work (I need to turn around the phone to make the red Rec button work) and when I try to watch the recorded video, the program cannot show it all (it shows a cropped picture). Maybe my phone struggles with this app.

Filmakr - this app does not allow me to change the resolution (correct me if I'm wrong and if I missed something). Also it is annoying that it tells me to log in every time I open it.

There is also Filmic and other apps, but most of them require iOS 10.0 or later and I wonder is it worth to buy them, since I will not use all their options. I just need to change the resolution and nothing else. I don't need to set the white balance or exposure or special effects or something too advanced.

Thank you for your suggestions