Item 1 & 2 - The PP & Bomex engine covers will prevent rain from wetting your engine bay (unless the rain falls 90 horizontally), looks cool, will help to expel more engine heat due to aerodynamics, lighten the engine cover
For Bomex the center bulge is higher and obstructs the rear view.
Anyway it is not a good idea to get moisture near the ignition system, electrical wirings and the fuse boxes.
Also note that the original engine cover was designed for intake rather than expelling gasses (vents are forward facing??)
Easy to install - Just rivet or screw onto existing cover.
It is advisable to remove the original engine cover vent areas for better cooling and weight reduction.