Please no spoilers though.

1) Which schools should I have my mage perk into and how far to take advantage of any cool new things in DB?

2) Is destruction as my main source of damage on adept going to cut it at high levels? I will use conjuration, but no dremora lords.

Thanks in advance.

Conjuration and Destruction seem good. There are new spells for both schools.

Isn't there some sort of new awesome cloak?

I don't know about that, but there are some new runes.

It's called Whirlwind Cloak I think, not sure what it's called, but basically is a wind cloak that sends anyone who gets to close flying away. Pretty handy for a mage who doesn't want melee enemies getting to friendly.

http://www.uesp.net/wiki/Dragonborn:Spells