I have 4 grease pencil objects. I am trying to get one to be displayed in front of the other ones but I can't find a way to do it. I could just pull it closer to the camera in the 3D space but then sometimes I get ugly white lines around the object. I don't understand how blender decides which grease pencil object to be on top and which one to be on the bottom. (not talking about the grease pencil layer order!)
In my experience several greasepencil objects are rendered in order of their creation. So the original gets rendered first then its duplicate then the duplicate duplicate and so forth. The only wa around this for me has been in the properties panel > Viewport display> "in front". Not sure if this works for renders but to animate it should be enough. And in the end you can render that part separately and add it on top.
I'm not aware of any other way this is currently possible other that using 3d space.