Assuming MV, which of the three cycling specific build phase (short power, general build, sustained power) alternatives would produce the largest improvement on my FTP?
I intend to add two of these blocks to my training plan. Maybe someone can suggest which of the three be more a ‘base III’ than the other two.
Unless you discourage me, I’m inclined to do the sustained power block first, then short power.
This depends on a lot of different factors, such as training history and experience. No one plan is “better” than the other. It just depends on the type of training stimulus you would most benefit from as the cyclist you are now.
You mention FTP as the primary driver. Is that your only goal? What cycling discipline do you focus on? Have you used the TR analytics tools to check your power curve and identify weaknesses? Which plan looks more fun to you? These are all important considerations.
Also, did you run through plan builder?
EDIT: sorry, missed your main question about which plan 
Nevertheless, you might find it interesting still.
Very useful, though. Thanks