How to change a text layer and smart object in one call using the Photoshop node api

Yes, use the documentOperation end point.  Supply the edits you want using the layers attribute on the options property.  

In pertinent part:

"layers": [
            {
                "edit": {},
                "name": "Text Layer Name",
                "text": {
                    "content": "Text Goes Here . . ."
                }
            },
            {
                "edit": {},
                "name": "SO Layer Name",
                "smartObject": {},
                "visible": true,
                "input": {
                    "href": "https://drive.google.com/uc?export=download&id=21",
                    "storage": "external"
                }
            }
        ]