You wanna save battery, not so focused on clouds, use around 1ohm.
You wanna have a more clouds and flavor, build lower around 0.5 ohms...
If you're on TC just keep within 0.05-0.2.
Like what Chia said, it's up to your personal preference and the limits of your mod. What I just said are references, you can use them as a baseline and adjust accordingly.
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