Mods

Newer player, curious about how to decide what mods are best for characters? Does each character have a specific combo of mods that most benefits them, or is it variable?

I am most curious about guys I'm using of course, such as Boba, Phasma, IG88, Vader, ST Han, and Kylo. But, I'd also like to know the method of determination so I can figure it out as I unlock more characters.