How to profile Unity FPS drops: CPU, GPU, or memory bottlenecks?

[Andrew31]

I'm an indie game developer working on a Unity project with a stylized 3D art style, and I've hit a major wall with FPS optimization as I've added more environmental detail and AI characters; my framerate tanks in certain scenes, especially on lower-end hardware. I've done the basics like reducing draw calls with batching and using LODs, but I'm struggling to identify the specific bottlenecks causing these dramatic drops. For other developers who have tackled similar issues, what are your go-to profiling tools and techniques within Unity to pinpoint whether the issue is CPU-bound from scripts and physics, GPU-bound from shaders and overdraw, or a memory issue? I'm also curious about practical strategies for optimizing shader complexity and managing real-time lighting without sacrificing the visual identity of the game.