Which position sizing method is more acceptable?

Hello to all present here… :pray:

As i am going through the position sizing chapter in varsity… I found that there are 4 ways/process of applying position sizing in trading…

  1. Unit per fixed amount
  2. Percentage Margin
  3. Percentage Volatility
  4. Percentage risk.

Among the above 4 i found 1, 2, and 3, little bit difficult to apply but the fourth one that is precentage risk is comparatively suitable… And this is one which is used by most of the traders i think so… And i know everyone have their own rules…

I just wanna ask which is the best one in over all scene and which one do you guys apply??