7.4v to 3.3v convert
The best choice depends on requirements you haven't shared.

If low cost is most important, you might use one of the diode based solutions. If spending more than $0.25 is acceptable, you should probably go ahead and use at least a linear regulator, rather than rely on diode drops.

If the supply voltages for your loads need to be set very accurately, or if the load currents vary dramatically (for example, they have a shutdown mode where they draw very little current), then you should prefer a regulated design over an unregulated one (just using diodes). 

If efficiency (or battery life) is important, you should consider using a switching power supply rather than any of your proposed solutions. 

If very low supply noise is important, you could prefer a linear regulator, or a switching regulator cascaded with a linear regulator.

Etc.