The objective of the proposed research in this thesis is to develop modeling, analysis, and control methodologies for grid-forming (GFM) and grid-following (GFL) voltage-source converters (VSCs) in hybrid AC/DC power systems. As inverter-based resources (IBRs) increasingly replace synchronous generators in power systems, existing modeling frameworks—which often assume idealized voltage conditions—fail to capture the complex dynamic interactions between the AC and DC sides, especially in multi-stage converter systems. This research first addresses these limitations by introducing decoupled and scalable small-signal models for AC-GFM/DC-GFL and AC-GFL/DC-GFM configurations, and then investigates the tightly coupled AC and DC dynamics in emerging AC-GFM/DC-GFM control architectures. The outcomes will enhance the understanding of converter interactions in multi-terminal DC (MTDC) networks, provide insights into stability trade-offs between inertia provision and DC voltage regulation, and offer practical guidelines for designing robust, interoperable control strategies in vendor-diverse hybrid AC/DC grids.