Looking for guidance with a workflow for live action+AI composited elements

I have live action footage that I'd like to add animated characters and background to. Some of the shots are panning, while the majority are static. I don't want to use my footage as a starting frame though, I want the end result to be my exact footage plus the AI-generated elements. I'm familiar with basic Comfyui workflows and have 2 3090s. I also have strong knowledge of After Effects and Cinema 4D. I'm also open to pay services like Runwayml. If someone could point me towards workflows that might work for me, I'd appreciate it.