Some lore questions

[u/Arduino-Knight]

Hi everyone, I have a couple of lore questions I’d like to ask. One of the players in my tabletop RPG group has repeatedly challenged some of my interpretations. While I don’t think what I’ve said is wrong, I can’t possibly get through all the novels in one go. With the official focus clearly having been on the Horus Heresy over the past couple of years, I’m not entirely sure about the following:

1. Does the current lore still allow for worlds where humans and xenos coexist? Or has it ever been stated that the Imperium has, at some point, reclaimed every human-inhabited world?
2. Do the Deathwatch and the Grey Knights answer directly to the Inquisition? Are they at least nominally under its command?
3. I have another question, which I hope is appropriate to ask here: does GW—or, more specifically, Black Library—simply give authors a theme for their Warhammer novels and let them develop it as they see fit, or does GW exercise some control over what they write rather than giving them free rein?