Depends on the layout of the room and where is good to place the projector for an unobstructed throw, minimise noise disturbance from it, etc. - personally I'd probably aim for around 4m or so and whatever zoom works with that.
Its a rectangle room with led lighting so nothing in the way. Back wall to front wall 5 meters. So il be sitting about 4.5 meters from the screen (allowing 1/2m for the sofa width). Does that help?