First, congratulations on giving it a try, Antonius 
As for your questions Tom answered all of them, I'd just add one thing regarding UI customizations.
As you know, with Creo PTC decided to ditch config.win as a way of keeping UI customizations and introduced file creo_APPNAME_customization.ui (so it's like creo_parametric_customization.ui). And they keep this file by default in profile directory, the same you can set with PTC_WF_ROOT variable. That way you can keep separate UI customizations for different versions of Creo even when you're not using Windchill.
I see it this way: if you're not working with Windchill and want to keep separate UI customizations for different releases of Creo (eg. Creo 2.0 and 3.0), setting PTC_WF_ROOT will keep them that way. If you want to have different UI customizations for different projects made with the same release (like Creo 3.0), config option Tom mentioned comes in handy. Of course you can always use load_ui_customization_run_dir without ever setting PTC_WF_ROOT and it will also work.
Actually I ended up recently with modyfing psf files in our classrom by adding PTC_WF_ROOT for every release of Creo and ProE just to be sure they won't share any UI customizations or Common Folders additions.