Best answer is to just jump in! That what I did!
Flexibility, alot more flexible compare to Morrowind. After one do this http://www.uesp.net/wiki/Daggerfall:Lady_Brisienna, granted if ya want to do the main quest, ya can do anything ya want afterward!
Size wise, the world is huge, but one should not run around in the wilderness; there is nothing there. Outpost wise, small as to village and huge as in cities.
Quest wise, there are many, but alot generic as well. Meaning, ya will find out that ya will do the same quest again and again, but from different quest giver. Main Quest is still different and Unique the whole way. Oh, and there are time limits in quest. Ya MUST do the quest with the minimal amount of time given (usually like 10-20 day to finish it), but ya will be able to finish the quest within a few days.
Dungeon is a WHOLE another story. Its HUGE! Literally. Ya can actually get lost in the dungeon real fast. Recall helps alot on going back to the entrance if one planted mark there.