Sorry ignorant newbie - saving a warp on smart layer

Smart Object layers operate much like a raster Pixel layer. It does not matter if the smart object layer smart object contains  many layers including vector layers and warped smart object layers and some are warped smart object layers.  Because of the way smart object layer work.  Photoshop renders Pixels for the smart object composite and users these as the layers content.  These pixels can not be changes by Photoshop tools or filters.  Smart filters can bet attached to a smart object layer and every smart object layers has ans associated layer transform recorded in layer that can scale rotate and distort the layer composed pixels by applying the filters and layer transform to the hardened Pixels rendered for the layers content. In the order smart filters were attached to the layer. Make a change and all can be reapplied in order starting from the hardened pixels render for the layers content. 

 Mockup are populated by replacing smart object layers content  or editing smart object layers content. Texture are usually added via a texture layer overlay blended into smart object layers and Smart displacement filters attached to a smart object layer.  The displacement map and texture overlay are for a fabric texture  and fabric contours and wrinkles not for fabric designs, logos  and labels. there in the object. Changing object within object complicate things IMO something you should aviode doing. Make and additional Smart object layer for the object you wakt to replace instead.

It is quite easy to design Mockups templates that can be batch populated with a Photoshop script.  A mockup template can be very complex but organized for easy population.   Mockups template can also be quite simple.

Every Smart Object Later has an associated layer transform. Layer are warped and distorted via a layer transform. Smart object layers transform are not actually applied to the layers object.   They are applied to the layer pixels rendered for the smart object layer.  If you update or add a smart filter to the smart object layer.  The Smart Object Layers associated transform will be applied to the pixels rendered for the layer.  Smart object layer's transform setting are recorded and associated  with the smart object layer so it can be reapplied should new pixels be rendered for the layer.   To do what you want to. You have to create a Smart Object Layer and change its layer transform to include the warping you want.     To use this warp you do not place images you either use smart object Replace Content or you edit the smart Object.  To use replace content the replacement Object needs to be exactly the same Size, Aspect Ratio and Print resolution as the originals smart object because the layers associated transform is not edited or replaced by replace content.  If you go with Edit Object you can not change the object size for the same reason.  The smart object layers associated transform is not changed  when you edit the object temp work file. The object size need to remain as is. You can fit image into the object editing the object.   Most Mockup Templates are updated via Replace Content or Edit Object. 

Place is used in Photo Collage templates where image are placed in sized, positioned and shaped.   Automatic  rotation and distortion  via smart object layer would not be supported for place create the smart object layer and sets the layers associated transform settings.  There are no existing settings.  Paste is also use to populate Photo collage template a pasted layer has no transform.

If you double-click the Smart Object you can put any other image inside that and on saving it the SO instance in teh containing document will update with the new content in that warp. 

THat sounds pretty much like what you aks, so what is your problem exactly?