Sorry not sure I understand your question about “how it runs to fill down?” If asking about the mechanics?
I have 5 hydras 52 on my tank, on average ~120w each - even though leds there’s a decent amount of heat.
I also run ~150w fuge light 18hrs and have quite a few pumps.
When I ran t5s i would always put a fan to disperse some heat. Even tiny usb fans were enough to save a few degrees. You can get cheap aquarium fans on amazon or use cpu fans.
My tank was hitting above 81 when I decided to get the chiller, haven’t had issues bringing the temp down even with lights on and no AC in the room.
I’ve been able to dial in the temp within ~0.8F with the chiller.