While copying or auto-fill the condition in conditional formatting, the reference cell remains a constant which becomes a hurdle when you want to apply a variable condition. This can be overcome by changing the constant to a variable by removing the $ symbol in the reference cell as below.
This works (for Excel 360) except when there is a formula. So, if the condition was =2*G3 the conditional formatting will not auto-increment the cell address as you drag the formatting down using the format painter