There are a few features which are common to most electro-acoustic guitars:
This feature is by no means unique to this type of instrument, but the majority of electro-acoustic guitars have a single cutaway shape, while only a minority of pure acoustics do so, perhaps because the resulting reduction in acoustic volume matters less with an electro-acoustic. A cutaway makes swapping between electric and acoustic instruments a little easier than it might be, though the very top of the fretboard is still left less accessible than that of an electric guitar.
Piezo pickups produce a very low voltage by comparison with magnetic pickups. A pre-amp is therefore required to boost this signal to the accepted standard instrument level, usually placed in the side of the body near the neck joint, facing the player. This does have some effect on the structural integrity and tone of the guitar some models therefore use a dedicated external pre-amp in the form of a belt pack or floor pedal.
Most pre-amps feature some form of tone control (typically a 3-band graphic EQ with sweepable mid frequency) and a blend control if there is more than one pickup. Recent innovations include the addition of an onboard digital tuner.