I am hopefully getting my 950xl delivered today. I am currently running a 920 on 8.1. Can I use a backup of that phone on the 950xl or should I just do a clean install and individually install apps etc and loose some data?
Going from WP8.1, I'd personally suggest going from fresh and downloading apps again (it's a great way of slimming down on apps you don't often use). With regard to potential data loss, it depends on what apps have that data. Personally speaking, any data I want to keep is on the cloud, anything that's app based, I can stand reconfiguring.
To be honest I don't know what 'data' I would lose if any as you say most stuff is cloud based (documents pictures etc). App bloat is probably a good reason to not to install a backup especially one from a previous os.