There's a ton of balancing/normalizing related stuff going on with the instances of the Gain plugin and all the effects plugins are tied to modifiers onscreen. As far as CPU usage goes, those plugins are incredibly lightweight so it's not a reason to be concerned and removing them wouldn't have a noticeable impact on performance.
What Gear do I need?
Troubleshooting Sunday Guitar
My instrument/controller isn't connecting
My Song-Specific Patch is Different from the Demo
Customizing Your Song-Specific Patch
Sunday Keys Version 2
Using the Tonic Pad Player
Getting Started with Sunday Keys for MainStage
Troubleshooting Sunday Keys for Ableton
Getting started with Sunday Keys for Ableton