All 20mm.
I'd hate for you to blow money on something you may not need. Make sure you go over the thread I linked to determine if you actually NEED shock spacers.
If you do, No problem. Will you have issues?
If you jamming another 5mm (Strut brace) under the shock spacer I'm going to say yes. It will be VERY close to the bonnet, and the deflection in the upper shock mount bushes as you drive over bumps might be all it needs to wack a dint in your bonnet. In fact, I recommended anyone running these as is that they should check clearances, as there are small differences in manufacturing tolerances, shocks and bushes (rubber vs polyurethane), it might clear one bonnet on a setup but will hit the next (although i've had no reports of any bonnets been hit yet)
You can easily avoid this by cutting the top off your Shocky, when assembled. Only a couple mm above the nut, then cut a slot in the top with a 1mm blade on an angle grinder that you can put a large flatblade screw driver in to hold the top of the shock still when removing/installing.
Go for a drive without your bonnet on and watch your shocky, you'll see how much they move when going over bumps. Plus driving without a bonnet is badass.