Guild Wars 2

Can I keep the items from the reward tracks if I put them in the bank after earning these with a demo character? Like Transmutation charges and other stuff.

This is easily tested, but:

No. Demo characters have a copy of your main character’s bank. In fact, they have a copy of everything, from achievement progress to reward track status. No demo progress, in any capacity, is reflected on your main character. (You can even burn through transmutation charges – it doesn’t matter.)

What I’d l like to know is if Anet would do us a solid if we happened to get an ascended or precursor drop… It makes playing demo characters at all a little nerve wracking, knowing I might lose out on the best possible RNG.