I have never used a neck angle. I have my solera built flat and my fretboard parallel to the neck, no tapper. However, I just had my first customer complain about a buzz from the 11th fret and forward on the bass strings. I have tried everything, the action is at its highest (4mm on the bass side at the 12th) and I lowered those frets just a little bit, and still have the buzz.
In this case, my only conclusion is that I should have had an angle on the neck.
I am going with the fretboard tapering option, as it will be easier to achieve. And I do not like the idea of tapering on the lower side of the fretboard to compensate the angle between he neck and the lower bout of the soundboard. Too much trouble. If that doesn´t work, I will modify my solera and give it a try.
Have anyone has any experience with this method of flat neck and tapered fretboard? It will be appreciated.