Generally, if the manufacturer is using electric slides, then each will have it's own switch because each has it's own electric motor. However, manufacturers that use hydraulic slides may have all slides operating from a single switch because it is less complicated (meaning less expense). Even that is not absolute, some brands and models may have independent switches for each slide-out.
So, if hydraulic slides, you will need to check out the details. But if electric slides then each slide out will be independant since running 3 or more electric motors at the same time requires too much power and they all won't reach the end of their travel at the same time and excess over travel is not a good thing to do.
Larry Day
Texas Baptist Men-Retiree Builders since '01
'13 Silverado 3500HD LT 2wd CCSB SRW, custom RKI bed
'19 Starcraft Telluride 292RLS
Rig Photos