All projects share a common engine architecture shown in Figure 1. This means that the engine object is 100% identical across all six synths. The only difference is in the SynthVoices that it uses in it's voice array. Note that the class name "SynthVoice" has been kept across all synths so that there are no changes needed in the engine.

Figure 1: SynthLab example synth common engine architecture

You can find information about the engine throughout the programming guide including:
Engine & Voice Programming
SynthEngine Object
SynthEngine Example