Modular Building Systems (MBS) are still in the phase of developing its popularity in the industry, with emerging novel designs. Initially, MBS walls and floors had been highly influenced by the Light-gauge Steel Frame (LSF) designs made of Cold-Formed (CF) steel studs, either as loadbearing or non-loadbearing types which have been extensively researched all over the world. However, recently the MBS practice in the industry tends to incorporate Square Hollow Section (SHS) steel columns for their improved structural performance and convenience at the manufacturing stage despite of the limited research knowledge in terms of the Fire Resistance Level (FRL). Moreover, catastrophic failures and fatal accidents are common with steel-based structures in case of a fire. Hence, the fire performance of loadbearing modular walls with SHS columns have been identified as a critical research gap. Firstly, Finite Element Models (FEM) were developed for the original modular wall, a Light-weight Timber Frame (LTF) wall and some LSF walls. The FEM analyses results very well matched with the full-scale experimental results so that the FEM techniques were confidently used to study the effect of variables chosen based on material availability options, cost reduction and construction practice. Structural and Insulation FRLs have been evaluated for the chosen parametric walls, where the produced graphs of structural and insulation FRLs can be referred to determine the adequate thickness of column sheathing and the Insulation Ratio (IR) respectively. The choice of non-loadbearing stud type can be evaluated against other limitations related to energy, cost and construction practice.