There has been an extensive modelling of the optical wireless channel, and the optimum modulation scheme for a particular channel is well-understood. However, this modelling has not taken into account the trade-offs that transmitter and receiver selection usually involve. For a particular type of transmitter, the modulation bandwidth and available power are closely related, as are receiver bandwidth, active area and sensitivity. In this article, we present a design approach that takes this device selection into account. The article details a general design method for an optical wireless communication system using a holistic design approach (i.e., considering channel, modulation schemes, and device constraints). The article shows results for particular examples, showing a substantial increase in margin (or data-rate) is available using this approach. For instance, by using this approach mutually optimising both modulation schemes and device constraints, it is found that for an optimally chosen Gallium Nitride micro-LED and a commercial photo receiver pair, a 20 dB SNR margin (or ~3 times data-rate improvement) can be obtained compared with a more typical approach mainly concerning the modulation scheme optimisation.