Swapping in some upgraded valvesprings on a stock timing chain is pretty simple. Any rocker/cam upgrades will gain from them although "required" is a strong statement. On bigger cam setups you are going to need extra room in the valvespring area to allow the cam to lift.

Also, lift does not play as big of a factor on the required spring strength as duration does. The more duration you have the steeper the cam lobe will be and the more succeptable to floating it is.