Btw, I'm on the way back from greybeards and just got attacked by....a dragon!! I'm only level 6!!
Personal preference and playstyle really. I have characters who use two handed, sword and board, just spells , spell and one handed and just one handed. I personally do really poorly with dual wielding but my son cleans up with it.
Personal preference. I like blade in one hand and summon spell in the other hand..
also bow for sniping and sneak..
Use whatever you like David -s-
You can encounter dragons from level 1, if that's the level at which you'd solve Dragon Rising quest (the one where you kill a dragon in front of the Whiterun). However, your level still playes a role, and as your level increases fun will increase as well.
I love bows in this game and use one for every character I have played so I build that skill up first.
Also don't just stand there swapping wacks with a foe learn to run away and use cover to your advantage.
Good Luck.