Tow-Based Discontinuous Composite (TBDC) is a class of materials that is manufactured by compression moulding with randomly oriented tows. TBDCs have demonstrated high-performance in terms of specific tensile strength and stiffness, while having a quasi-isotropic response in the plane, thus competing with composite laminates [1]. Prior research has focused on conventional TBDCs, with tow thicknesses between 0.12-0.25 mm. In recent years, new TBDCs have been developed using ultra-thin spread tows (down to 0.02 mm), displaying different mesostructures and expanding the design space. However, different parameters, such as the tow thickness and the volume fraction of resin pockets, have been shown to affect the stiffness and strength of TBDC plates [2,3], which is a major challenge that remains to be addressed in the modelling of material systems with ultra-thin tows. Gulfo et al. [4] developed and validated a voxel-based method using random sequential absorption to generate 3D mesostructural models of TBDC plates. The current work utilises the developed methodology for predicting both elastic properties and strength for three baseline cases, including thick, thin, and ultra-thin TBDCs. In addition, a parametric study is carried out to investigate the effect of critical parameters such as the tow moduli (up to ultra-high modulus), tow dimensions, plate dimensions, and preferred in-plane fibre orientation distributions induced by the manufacturing process. Design constraints are found in terms of their quasi-isotropic in-plane response and critical plate dimensions. Finally, comparisons with simplified methods such as short-fibre models and equivalent laminates are also presented. The results show opportunities for optimising the stiffness and strength of TBDCs, considering very thin plates and ultra-high modulus tows, which are of interest for future applications in thin-walled composite structures.