Does anyone know the difference between QS7133-840 and QS7121-840?
QS7121 is the old no longer produced model of the Hardwire 16.
The Hardwire 16F is the one you want. QS7133
Which board is contained in the QS7134-840?
Same as the QS7133. It is the IQ Hardwire 16F (the current version).
QS7134 is just the one that comes with a large enclosure which can fit the backup battery.