1. I don't think it makes a difference at this point. At least it hasn't for me.
2. I understand starting new as a way to eliminate things you don't use, but I have some apps that do not back up their data anywhere, and I'd lose that data, in some cases many years of data. And there's always the offload apps function, either done by iOS or done manually by the user. FWIW, when you offload an app, it keeps the app data locally and leaves an app icon with a little download arrow so that you can easily reinstall the app if you need it - and maybe also so you don't forget that you offloaded it.