To get the best temperature on water-cooling, always consider the ambient/room temperature. The closer to the room temperature in correlation with the CPU temperature, the better. Our components, like high or low RPM fans, depends on the fins per inch of radiators which is also “the more, the better”.
It is also better if you have intake and exhaust on the casing of your cooler. Even though you’re on LCS, if the airflow on the case is not good enough, the end-result won’t still be good enough. One intake would not be enough to cool the flows on your tubing. It is also advisable to have probes to check water temperature.
Next would be the utilization of the inlet and outlet of the water-block. We should be following it because there are small tubing inside the block and the flow should be on right direction. If this is not followed, there will be a build up of heat inside the block because of the restriction so the flow must really be on the right direction. This is base also from the statements of watercooling users from different forums. Long tubing also affect the temperature. As much as possible make short loops only. Check also if there are kinks on the tubing.
And lastly, make sure there is no air inside the loop to maximize the water-cooling setup. To eliminate the air, just tilt the case from different angles to remove the bubbles and go to the reservoir.