Wave Energy Converters (WECs) are deployed in arrays to improve the overall quality of the delivered power to the grid and reduce the cost of power production by minimizing the cost of design, deployments, mooring, maintenance, and other associated costs. WEC arrays often contain devices of identical dimensions and modes of operation (homogeneous array). The devices are deployed in close proximity, usually having destructive inter-device hydrodynamic interactions. However, in this work, we explore optimizing the number of devices in the array and concurrently, the dimensions of the individual devices (heterogeneous) to achieve better performance compared to an array of identical devices (homogeneous) with comparable overall submerged volume. A techno-economic objective function is formulated to measure the performance of the array while accounting for the volume of material used by the arrays. The power from the array is computed using a time-domain array dynamic model and an optimal constrained control. The hydrodynamic coefficients are computed using a semi-analytical method to enable computationally efficient optimization. The Hidden Gene Genetic Algorithm (HGGA) is used in this optimization problem to enable the possibility of changing the number of devices when searching for the optimal arrays. Tags are assigned to genes to determine whether these genes are active or hidden. An active gene represents an active WEC device in the HGGA-heterogeneous array, while a hidden gene results in a reduction in the total number of devices in the array compared with the homogeneous array. The total volume of the HGGA-heterogeneous array is constrained to be close to a given fixed volume. In the simulations presented in this paper, the HGGA-heterogeneous arrays were found to perform better than homogeneous arrays.