1)  I'm mostly into discord for OOC banter and not so much interested in them for any serious RP purposes.

2) Since Starfinder came out I've been kinda interested in the idea of a more hi-tech sort of theme set using the base 5e ruleset.  That being said, I'm also traditionally very interested in high fantasy.

3) Moral dilemmas and role-playing are prolly my top two, mostly because I've found that I just sorta like playing characters instead of just bland stat blocks that are meant to grind against other stat blocks until one or the other gives.  Beyond that, I suppose I'm a fan of exploration, since it often helps to facilitate the other two.

4)  I do love active NPCs.  They let you banter about even when other players are busy or not interested and often seem to help keep the party gentle guided towards the plot train without the DM having to do anything too heavy-handed.  That being said, I also tend to prefer that they lag behind the PCs a bit in terms of level, so that the PCs still do stand out as the stars of the story and not just minor supporting cast to the DM.

5) Frankly, it depends on the group.  I would tend to say smaller, for the simple reason that big groups take forever to get through each round of initiative.  On the other hand, if the party is allowed to be split and the different characters intermingle back and forth while out on different tasks it can circumvent that problem.

6) [s]NO NEVER ABSOLUTELY NOT[/s]  Fine by me. XD

As far as RBWY, I know nothing about the setting beyond the knowledge that it exists, so I don't really have any strong feelings on the matter.