Completed the demo, tank you very much looking forward to release.
Levels are useful (the testers tend to beat the game around level 30) but aren't a guarantee. Equipment is also really important, so playing the game with an extra high level is only going to make the next few areas easier, but not super duper easy. Still, if you're looking for a challenge then you can restart. It only takes about 20 minutes (if you know what you're doing) to clear the demo's content without grinding. You can actually beat Quinn at level 1 with some luck!