how to design a doherty amplifier
I recommend this reference
S. Bousnina, “Analysis and design of high efficiency variable conduction angle Doherty amplifier,” ITE antenna & propagation journal, vol. 3, no. 3, pp. 416-425, April 2009.
It shows how to design an asymmetrical Doherty amplifier, how to bias the main and auxiliary amplifier, and how much power is expected from each asymmetrical Doherty amplifier configuration. The same principle can be extended to the design of three-way Doherty amplifier.
Regarding the LDMOS devices, it is better to use transistors with low output parasitics (including package capacitance). That way it will be easier to reproduce the resistive load pulling effect in the Doherty amplifier.