Cummins Timing

Been studying timing a little and had a few questions about timing a performance build with a bigger set of turbos and bigger fuel. I hear negative timing is the way to go to help spool turbos up faster which would make sense to me but i also hear adding timing also helps. Interested in what you guys have found to work the best for you. Another couple things ive been wondering is the max timing you feel comfortable running these engines at and what timing do you normally run at idle on a bigger injector truck lets say 100%- 200% over? Any input helps just trying to learn. Thank you