2) ...you would be better off venting the tubing in this case at the top as it will bring you closer to a taps on drops to buckets flow rate )
There is almost never a good reason to vent maple tubing. 1) You will lose any natural vacuum that might develop. 2) Venting pulls in air which contain microbes, which leads to faster taphole drying. Venting has been shown repeatedly to result in lower sap yields. The key is to have a slight amount of slope. Some liquid retained in the tubing when the run stops is normal in most cases.