it is referenced from disc or loaded. The viewport is raytraceing all the time. like cycles. so it dosn’t matter how much stuff there is in it because it will work smooth anyway. the diff is. that cycles can only raytrace like rendering stage. and clarisse raytrace like clay view wireframe view etc. and displays gizmo on top of that.
Blender have kinda similar technology. if u have object in one blender. just save the file open other blender. and simply link the object to your from blender from the one u saved. it will work very similar. However… clarisse have way way more better optymalizations and 1M polygon in clrisse is tottaly diffrent compared to 1M polygon in Blender.
Also clarisse was writted with multithreading in mind every single thing in this app is multi threaded if it is not possible to make something multi it will be not implemented. this is for example reason why clarisse dosn’t support fbx. because fbx can be only single core.
also because of raytraceing if u apply displacment on something it is displayed instantly at final form same is with bumps and normal maps… and if u add for example scatter to scatter tree u can tell scatter to scatter on surface of the displacment.