1. As Stabbey said it likely won't be anything you can put off. You're in a war an need to secure an alliance to improve your legitmacy as the Emperor's Bastard. What with the quest structure as it is the team would need you to make a choice at a given time in order to allow the game-world to adapt to it. Like if you were close to beating the game but then decided to marry the dwarf princess would you still be able to do her quests?
And as Stabbey said there is essentially two aspects to the marriage: Romance or Politics. You will gain rewards either way but it will be a choice between the Princess' agenda which may go against the wishes of her faction and improving your lot with the faction. Take the Undead Princess.
Princess Ophelia is reportedly not happy being an undead. Having once been among the living she wishes to return to full life. You may marry her to gain the support of one of the most powerful factions in the game but you will have to decide if you want her to be consigned to her fate of undeath - or help her. This will involve some difficult choices but if you choose to help her she will somehow be brought back to life as an attractive human woman (the only one you can marry in the game). This will enrage the undead, many of whom have accepted their condition and even melded it to their religious beliefs - thus you will see a major decrease in contentment with their faction.
2. Yes you will be able to customize your dragon appearance in single-player and multi-player both aspects and looks of the dragon, in fact if you look at the front page there is a promotion featuring a gold jetpack.
Beta Question:
They are having in-house beta testing in Ghent.
