Dont know which one that im suppose to use

[Tuxxen]

Which one of these am i suppose to use in fortnite you have Targeting sensitivity and then targeting ADS but you cant ADS with a gun with no scope? 

[DPI Wizard]

Targeting is anything that is shoulder aim without any zoom (the camera just moves closer).

ADS is shoulder aim with a little bit of zoom. See this gif, from hipfire, to targeting, to ADS:

How this works is based on the class of the weapon I think, so I'll see if I can add it to the descriptions.

[Tuxxen]

nice thanks!