This is so odd to me but it could just be our differences in vaping styles. I would normally run a .25 to .15 ohm build at 3-4 volts and get a nice warm vape. At .6 ohms I run at 7-8 volts. Currently running 1.6 ohms at 11 volts and taking deep vapes.
Also note that @SthrnMixer runs a .6 ohm build at 10 volts but he likes to take 1 to 1 and a half second vapes.
I guess it is different for everyone. If 4 volts is comfortable for you then go with it. Your set up and mine isn’t far off on amp draw, 6.88 vs 6.67 but our wattage varies by 50 watts.