Lightforged, not “Lightbound”, that’s just a group name.
It’s not the same; given their vastly different track records and goals (for one, Turalyon and Lothraxion challenge Xe’ra on a Light-related matter, she compromises. Anyone challenges N’Zoth on a Void-related matter, he harms them), I’d trust Xe’ra over N’Zoth any day.
Not everyone. Also, I wouldn’t express objection through killing. Illidan was strong enough to break free, he didn’t need to kill. Finally, killing you allies’ leader in the middle of enemy territory is dumb.