1. I want to say no, but if it is present rare is pretty much the best option imo.

2. Mixed races for sure, always makes things more interesting.

3. I think preexisting setting sounds fine, though I'm not to sure what you mean

3.1 'Feel' of the setting (pick 2), the genre if you will: 

classic fantasy or high-fantasy I feel is most flexible without giving ppl access to world destroying technology. 

3.2 List your top three custom universes:
Tolkien
Eberron
Forgotten Realms

4. Nation construction:
4.1 What is your opinion about being presented with a list of factions to choose from? 
I don't like preexisting factions to choose from, too binding. Giving ppl some freedom helps create more interesting diversity. 

5.1 Would you prefer a hard system (list of traits, flaws,...) and fixed set of rules to resolve IC conflicts? 
trait systems are good, but to many rules turns some NRP's too much like a video game.

5.2 Would you prefer a more mathematical approach or free-form policy for ingame events?
Refer to last answer.

6. What is your stance on the use of dice?
I think having dice as optional should be good if players can't decide on an outcome.