A large-scale integration of renewable generation,usually interfaced to the network through power electronics,has led to an overall decrease in power system inertia. This paper presents novel insights on the fundamental stability properties of such systems. For that purpose, a uniform set of Differential-Algebraic Equations (DAEs) describing a generic,low-inertia power system has been developed. A full-order, state-of-the-art control scheme of both synchronous and converter-based generators are included, with the latter differentiating between the grid-forming and grid-following mode of operation. Furthermore, the dynamics of transmission lines and loads are captured in the model. Using modal analysis techniques such as participation factors and parameter sensitivity, we determine the most vulnerable segments of the system and investigate the adverse effects of the underlying control interference. Finally, the appropriate directions for improving the system stability margin under different generation portfolios have been proposed.