Adjustment layers applied to smart objects

When ACR is working on a Jpg or Tif  image or you are using the ACR  plug-in to filter a layer as a filter or smart filter ACR is not working with your Camers RAW data in these cases.  ACR is working on a Post processed image or some pixel layer you created. There is no RAW data.

If you want to edit in a non destructive fashion in Photoshop you need to understand how Photoshop works and use new layers when you need to.

Only RAW file have You Cameras Sensor RAW data... A smart Object can contain a RAW file object. ACT cam Open and RAW File as a smart Object instead od a Background image layer.   You would reprocess this object through ACR by double clicking the object in the layer palette.  The will open the RAW object in ACR Plugin.  It makes no difference if you open it from lightroom into Photoshop or Open it from Photoshop.  Lightroom does not supply a Photoshop Plug-in to Process its RAW conversion settings.  ACR is used in Photoshop.  Lightroom and ACR use the same Adobe RAW conversion engine.

I do not install Lightroom for it does not support layers.

I'm not sure you understand how this works. You don't use the ACR filter on a smart object - you double-click it to open in the ACR raw processor. These are two different things.

The ACR filter is just another Photoshop adjustment on top of the raw file, just like curves or any other adjustment.

Yes, you should always do as much as possible in the raw processor, before additional RGB adjustments in Photoshop. You have much more data to work with in the raw file.

Smart Object layers pixels can not be changes with  Photoshop tools the can only be acted upon via Smarty Filters, Smart Object Layers associated layers transform and Adjustments layers.  Smart Filters are applied in the order they are added to the smart object layer. And Adjustment layer applied in stack order. 

So Photoshop Renders Pixels for the object to use as the layers content.  The pixels are transform by the smart object layers associated transform to size position and distort the object composite image view.   Then the smart Filters added to the layer  woul be applied in order added on the layers to filter the composite view then   the adjustment layer effects are done is their stack order. 

You need to understand what Photoshop is doing.  For example if you use ACR as a Filter on a pixels layer that layer pixels will be changed  a very destructive process.   If you had first covered that pixel layer into a smart object layer.  Using ACR file on a smart object layer  make it a smart ACR filter.  Pixels are not actually changed  you can redo the Smart filter of remove it.

You need to understand how Photoshop works. Some Process are very destructive like painting  cloning healing.  However you can clone,  Heal and paint into new top empty layers and  not be destructive.   You can Stamp visible layers and blur, burn, dodge etc in a not destructive manner.   How you edit is up to you Layers are very helpful.....