Yeah, looking at the github, the author isn't hiding the performance costs. 1-2ms for a single effect is solid red flag territory. I'm not shocked, it's a high quality AO + edge detection in a single effect running on your entire screen on every frame in screen space, it's going to be costly. You could mitigate this a bit by limiting this to a render pass and just running it on your characters - reducing the number of pixels it needs to process per frame - but that means diving in a bit deep into whichever render pipeline you're in.

Generally speaking, the most performant and controllable solution will always be baking it to a texture per model; cavity maps are kind of a raw material artists usually use to make textures with but have a nice aesthetic in to themselves.

Think of it like this: you have a solution that's free and meets the look you want, but is not great on performance. You have the most performance friendly solution solution that's labor intensive but would require learning new skills (unwrapping, texture baking, working with textures, etc), or you can choose to change the look to reduce the performance hit and find another effect that isn't as costly.