Why 240p, 360p, 480p, 720p, 1080p ?

The web video script I'm looking at getting apparently saves an uploaded video in 240p, 360p 480p, 720p and 1080p, via ffmpeg.
That seems like overkill and it seems that it would take up a lot of disk storage to store 4 copies of each video.
The uploaded videos don't have to look state of the art when viewed. If I wanted to reduce the potential storage, if I were to modify the ffmpeg to not upload so many version the each video, which resolution(s) would be best to keep? What is the downside…

Why 240p, 360p, 480p, 720p, 1080p ?

Can the iPhone XS or iPhone X record screen at 1080p via QuickTime?

I need to record some gameplay of my app at 1080p, and I am considering buying an iPhone XS or iPhone X to do so. I currently record the screen of my iPhone 7 via QuickTime for better quality, and the output is 750×1334, matching the resolution of the iPhone 7.

Before I commit to buying a new iPhone, I wanted to confirm whether I can record the screen of an iPhone X or XS via QuickTime at full 1080p. Anyone know of this is possible? Thank you.