I think the amount of CPU used by messages should be rather minimal, BUT if you open 50 effects as they are, with the GUI attached, then the GUI redraws from all 50 modules is going to drain a lot of CPU power.
Most of these patches have a subpatch with the audio guts, so if you want to use so many at once, it might be an idea to separate out just the audio section, and then use a generic GUI that can be switched for all your effects. It's a lot of work, i know...but if saving CPU is your goal, then it would be the best way.