-tt set target GPU temperature. For example, “-tt 80” means 80C temperature. You can also specify values for every card, for example “-tt 70,80,75”.
You can also set static fan speed if you specify negative values, for example “-tt -50” sets 50% fan speed. Specify zero to disable control for some card(s).
Unfortunately, AMD blocked underclocking for some reason, you can overclock only.