Luff tension is important
Most people with roller-furler genoas simply leave the halyard cleated off all year. It’s one less thing to think about. But if you can get into the habit of adjusting it for different wind conditions, your boat will go upwind much better. Tighten it in stronger winds, to remove the belly from the sail and pull the draught (deepest part of the curve) further forward, and loosen it in light winds to remove the knuckle from the front edge of the sail. You’ll notice the difference!