Multiple Mesh Warps In One Project

Mesh Warp always covers the entire layer, but the mesh is always the size of the layer frame. If you have a 200 X 200 layer in an HD Comp and apply Mesh Warp to the layer, the mesh will only cover the layer, but if you have a layer that is twice the size of the comp or an adjustment layer twice the size of the comp, the mesh will be the same size as the comp frame and only affect pixels inside the frame. 

You can apply Mesh Warp to each layer differently or have multiple layers below an adjustment layer and apply the same mesh to multiple images.