If you need to put in a flat sequence structure to make things execute in order, yes, do that. You may not actually need a flat sequence. Remember that if you wire up the error terminals, that will enforce the order of execution of the different functions and VI's. All of the serial (configure, read, write) have error terminals, as well as the property nodes. So if you use them, a flat sequence structure is probably not necessary.
I recommend googling to learn more about hardware handshaking and null modem cables. The instruction manual for your device should tell you what kind of cable you need, and whether you need to use hardware handshaking
