No General rule.
These "two times more" was relevant to prehistoric configurations with 256MB, 512MB RAM, etc.
The swap file is needed in order to applications do not kresilas from OOM.
If you have lots of RAM, and you rarely reach the limits, then you can leave a small number of 512Мбайт - 1ГБайт.
If you have little RAM, and you constantly get beyond it, then the swap file to compensate for this missing difference is necessary (to you) amount of memory.
a small amount (~0.5 x RAM) that the OS started using the swap file for no reason.
The size of the pagefile
has no effect on when it will be used.
If you want to avoid using it at all, then it should be easy to disable.