Guild Wars 2

Is Fractal Daily Chest per character or per account?

And also how much pristine fractal relics does lvl 20 or higher fractal gives?

Chest is character and tier bound. If your elementalist has personal reward lvl of 30, he can get lvl 1-9 chest, lvl 10-19 chest lvl 20-29 chest and lvl 30-39 chest during one day. If you also have a mesmer with personal reward lvl of 17 you can get a total of 6 chests, 4 with ele and 2 with mesmer. The amount of pristine fractal relics will be 1 in higher tier chests, just like in lvl 10-19 chests.