How do the "Camera" and "Main Camera" blocks work in the VFX Graph?

Hello, I would like to understand how the "Camera" and "Main Camera" blocks work in the VFX Graph.

I want to implement dynamic smoke that will not pass through objects. To do this, the VFX Graph has a parameter in the "Update" block "Collide with Depth Buffer". This depth buffer can be transmitted through the camera, but since the character's camera is always moving and at a certain moment the character may turn away from the smoke and the camera will transmit incorrect values ​​of the depth buffer, which will cause the smoke to pass through objects and with a sharp turn we will be able to notice this. I want to add a camera for the smoke that will forever monitor it and transmit information about the depth buffer for this smoke, but when in scene 2 cameras everything starts to work incorrectly because I do not know how the "Camera" and "Main Camera" blocks work in the VFX Graph 'e. How can you ask a specific camera or if you have other ideas, I will be glad to hear.