Linearize Color Space

Thanks for the clarification! Honestly AE documentation on color management is kinda confusing.

Graphics and 3d don't need to linearize. It's for vfx and footage. The original graphics being produced in AE only need to have 32bpc if you want best lighting. Linearizing is for film fx and workflows. Don't make your graphics burdened by linear color space. Just preserve RGB with your graphics and change to 32 bpc if you are using light blooms and lens blur effects. Normally you won't need to go higher than 16 bpc unless you are using lots of lights and lens flares. Then you need to adjust and set your blend modes to screen rather than add. Add blend mode is just a fake screen mode when you aren't in 32 bpc.

The managing color doc is a bunch of jargin that just shows how film footage has never been well regulated for vfx for footage. There are old docs that bloggers posted on forums and AE just copy and pasted it into their forum and site. Linear workflow is not a well accomplished task in AE so don't clutter your workflow with it unless you absolutely need to finish in linear space for film.

So for 3D renders definitely always work in linearize color space

Why would you? Unless the 3D rendered files are already linear, this has zero relevance. Even the best 3D renderers spew out images with Gamma bias in their default settings or when using specific image formats. I'm afraid you are looking for a simple answer that doesn't exist and are only seeing one side of the equation. That and of course throwing around vague terms isn't really helping. An awful lot of "2D motion graphics" is actually 3D stuff in disguise. If you wnat a satisfactory answer to your question you will have to be specific about what you want to do, which source footage you use, what the output will be. There's no general recipe here and linearizing the color space has no inherent magic. For any of this to even become relevant, you will have to have specific blending operations in your comp that could benefit from a Gamma-free value range and about the only time when that happens is in 32bpc mode, anyway.

Mylenium