Thanks everyone for opinions. Let me contribute my experience for other newer people.
I finally got the regulated box mod, Siglei, and tried to build between 0.6 to 1.5 ohms, and set wattage between 10 to 16 w. Yes, higher wattage = better vape. It's produces a little more vapor but more important is warmer, hit harder, feel closer to the real cigarette.
Disadvantages: harder to build the coil, if coil is not perfect, it will burn/harsh. Go through juice and battery lot quicker. Mesh burn a lot quicker too. I used to vape at 7 to 9 w and could reuse the mesh to rebuild for a long time. But now, the mesh is burn bad, I only can reuse the mesh for several builds.
Do I like to stay at this higher wattage? Yes, between 12 to 16 w