Inverter-based resources (IBRs) such as photovoltaic systems and wind farms are being integrated into the power grids as part of climate change efforts. Most renewable resources utilize phase-locked loop (PLL) to establish network synchronization, and operate under the grid-following (GFL) mode. However, it has been recently reported that with the increasing amount of IBRs to replace fossil-fuel based synchronous generators, the continued use of GFL will reduce the overall stability of the grid. This issue can be resolved by changing the control mode of some inverters to grid-forming (GFM), which the PLL loop is replaced by a droop control loop. Nevertheless, the question regarding the ratio of operating IBRs under GFL and GFM in maintaining system stability has yet to be answered. This paper aims to fill this gap. We first built a high-fidelity simulation model consisting of only GFM and GFL inverters followed by extracting the stability features from the time-domain current and frequency waveforms of individual inverters. Next, an entropy weight method (EWM) is proposed to build an objective evaluation model for assessing the grid stability. Numerical studies were conducted to assess the stability due to different ratios of GFL and GFM along with different grid topologies and IBR locations. Overall, this paper serves as a guide for future placement strategies of distributed renewables within power grids.