Any of the go-to dedicated temperature controllers (Inkbird, etc.) will have switchable outlets for the heater and then a remote temperature probe, so you'd put the always-on heater on the outlet and the temperature probe in the tank somewhere for it to decide when to switch it on.
If you have already had a low power heater in there and it's been too much, though, I would look for an even smaller one. While a smaller heater will have more trouble compensating for very low ambient temperatures (if the heating goes out in the winter, for example), if you can pick one that doesn't get too hot (maybe low to mid 80s?) when just always on, you have some extra insurance against a controller failure - though a failure on a dedicated controller is far, far less likely than the failure of a built in heater thermostat, which is relatively common.
76-80 is a little swingy for my tastes, but any of those temperatures would work. If you have confidence that your room temperature won't fluctuate too much (no one likes really hot or cold indoor temps, no drafts or direct sun nearby, etc.), then it will probably do. If it's really your lights adding the heat, you could try to increase their ventilation too, but there's a chance extra airflow around the top of the tank will also increase evaporation (cooling, but also ATO consumption).
