I have personally worked with HTC , Samsung and Apple. What I noticed is Apple support , response , eco system , integration,customer approach and how the respond is far better than any other brand. I use pixel and iPhone currently.

After multiple repair if the issue persists, Apple will replace whole unit.

I have used 6 models of Samsung. 4 models of HTC and 3 models of googles Nexus and pixel. One plus.

All I can narrow down is Apple quality and support is much better

S2 with custom ROM

Nice of you to get him iPhone. I would recommend iPhone 11. If you have iCloud add him under family sharing so it will be easy to restore and guide him whenever needed

It’s awesome. Only thing I noticed certain app developers are way to slow to optimize the app to read and run all cores so it is heating up. Like Meta apps , certain VR apps.

Again most days I get through the day. But if on constant video calls or voice call for longer period the battery definitely drains faster.

Log into one drive from computer and delete the ones you don’t need empty them , understand this any and every cloud storage is a mirror sync of what you have if you deletes , unless you create additional folder and move the files to those folder.