Does a higher resolution show more of the world, given the same aspect-ratio

My source (via the Wiki) for this is in French, but it should work something like this:

Are they going to include a day/night cycle?

Yes. The cycle will be faster than real time. Events and monster spawning will change based on the time of day. Centaurs might attack a camp at dawn, and ghosts haunting an ancient battlefield might only be visible at night. Currently, the cycle lasts 2 hours with 80 minutes of day and 40 minutes of night, but this is subject to change before release.

Sylvari glow at night.

The Guild Banners are clickable by anyone in the world and act as advertised.

I say this from personal experience; I once found one at the exit from Rata Sum, which was a pleasant surprise as I went to leave.