A theoretical tool, the soft-SAFT equation of state combined with the Free-Volume Theory (FVT), is used for the calculation of thermodynamic and transport properties to (1) discriminate among discrepancies observed in different experimental data sets, (2) evaluate its capacity of extrapolation and predictability by comparing to experimental data, and (3) explore phase diagram regions where no experimental measurements are available. The well-known [C(n)mim][BF4] ILs family is chosen as a case study. Once a simple but reliable molecular model is proposed for this family, the density of several [C(n)mim][BF4] compounds is predicted using correlations of the molecular parameters as a function of the molecular weight. A comparison with different data sets showing discrepancies is addressed from the modeling results. The density of these compounds at high pressures is predicted and compared to the available data. The exploration of the phase diagram region is given by the study of immiscibility gaps in CO2+ [C(n)mim][BF4] mixtures. Finally, the viscosity of these fluids is addressed using the equation in a systematic way, and the behavior of ILs mixtures is predicted in agreement with experimental measurements. It is intended to demonstrate the synergy between experimental and modeling work.