SolidWorks Tips&Tricks - Lightweight components
In this tutorial you'll find how to reduce the CPU usage using Lightweight Components.
You can load an assembly with its active components fully resolved or lightweight. Both parts and sub-assemblies can be lightweight.
You can improve performance of large assemblies significantly by using lightweight components. Loading an assembly with lightweight components is faster than loading the same assembly with fully resolved components. Assemblies with lightweight components rebuild faster because less data is evaluated.
Answered with a tutorial: https://grabcad.com/tutorials/solidworks-tips-tricks-lightweight-components
On my opinion all parts must exclude fillets and chamfers, weldbeads - make a that kind of configuration. It's not a problem to see in assy mode, but problem come when you wish to make a drawing of that kind of assembly. My current work consist over 35000 pieces - fasteners not included , I'm not to unsupressed all assyis subassyis and patterns. If I do, I estimate over 50000 pieces. Number of parts rapidly growing when you use a features in assy mode as linear or circular or feature multiplying patterns of parts.