You don’t need pax count or final weight (unless bumping up against a limitation) before leaving the gate. You have planned weights based on what load planning has scheduled for the flight. If you are right at max taxi weight, you wait for final numbers before pushing, if not you taxi out and don’t take off until you have your final weight manifest, verify the weights, pax count, and takeoff performance. If the final fits the plan, you go. If they don’t, you send for new performance data.