I have layer 'states' on Geoserver for which I need multiple GetFeatureInfo templates. I would like to use that layer a couple of times on different maps, but I want different data in Leaflet popup. Is it possible to define multiple templates for same layer? Is it possible to select template name in GetFeatureInfo request? Is there any way to select template?
No - I don't think it is. There are two fixes that come to mind:
1 - copy the layer and add a new FeatureTemplate to the new layer.
2 - return all the data that any of your popups need and write some JavaScript to set up the pop up with the content you need.