In World Editor, press View > Physical Bodies (or Ctrl+Shift+P) to view the physics.
Convex is for dynamic meshes (those that move) and Static is for static meshes (those that don't move).
16 and 32 represents the total number of vertexes that will be used to create the physical body from the mesh. The higher the number, the more precise the collisions will be.
Convex physical bodies cannot contain any holes, so if your mesh has a hole in it (a donut, for example), the physical body will not (meaning that nothing will be able to pass through that hole). If you wish to keep any holes, you must use Static. This will, however, force the mesh to be static (i.e. it can no longer move).
If you switch to the Model Editor, load in a mesh, then press the Physics tab on the right (or press 4), you can then click on the Physics button in the sub-menu and see all the available ways to create a physical body. Creating a Convex physical body this way allows you to have 16, 32, 64, 128, or Max vertexes.
In terms of fewest resources, I believe Convex 16 would use the least, followed be Convex 32, and then finally Static, although I may be wrong about this. However, it makes sense this way. The lower the amount of vertexes, the lower amount of hard drive space it will take to store the physical body and the lower amount of RAM it will take to load it.
Btw, 10k seems like an awful lot for a rock. It must be a very smooth rock.