Ditch the top off system. It’s the weakest point of the system.
Make sure you position your sump carefully. Depending on any magnetic mounts for probes or float switches, Red Sea just doesn’t give much room beneath that stand.
What lighting? Again, the stand. Sump side is sealed and allows little airflow from outside the stand. My t5’s rum warm and even with a fan and 2 computer fans pulling In fresh air I have to leave the doors open to keep temps below 79.
Good luck and make sure to level all the feet before yiu fill it. You may have to reach areas that require you to lift the stand.