As I mentioned above, for stop-losses IMO the best way is “by price action/SR” (i.e. just above/below swings-high/low) and the second-best way is “by numerical volatility (e.g. an ATR-multiple).
In some platforms the default for ATR is set at 14, and in others, 20. It doesn’t matter much, as long as you understand (as with any indicator you use!) what ATR is, what it’s actually displaying, and why.
In his beginners’ textbooks, Van Tharp always suggested 2 x ATR for a stop-loss, and used that multiple as the example in the backtested examples he provided.
The only person.I know who uses that method uses 2.5 as the multiple.
Nobody can tell you what will be best for you. It depends what you’re doing. You have to test it for yourself. You have to know how to do that.
This very helpful post should be useful for you, and enable you to avoid some common mistakes! 