ip air questions

hi, im thinking of upgrading to iphone air from my android, but i need some questions, maybe some of them are in general in iphones but some are specifically for air

1. will mono speaker be enough for youtube and tiktok?
2. will 256gb be enough if i dont take a lot of photos?
3. hows the battery will i need to charge it when i average 8-9 hours of screen time?
4. do i need the case for it?
5. does it overheat?
6. is it worth it for 5+ years of usage