Yes hip throws are definitely more efficient when you close the distance. I would say both the distance and angle are established in your setup phase of the hip throw (when you start the throw). Lets say hip throws take at least 3 turns to execute and the first one is your setup and the most important.

Theres different setup approaches but i think a good one is to 'hop' into your opponent meaning you let go of your floor contacts and pull yourself into your opponent to close the distance while simultaneously you are turning away to load up your throw.

As far as angle goes your base foot will determine the angle of your throw. Lets imagine the starting position and imagine the arms are pointing in the x-axis direction and the toris are facing in the y-axis direction.



Now if youre throwing your opponent to your right you want to land your base foot inside the left quadrant on your opponent's side of the grid. The closer to your opponent gives more power while the further makes the throw safer. I think the sweet spot is the 45 degree mark that i drew in green.