When you are talking about "Configuration Properties", do you mean "Properties" or "Configuration" table?
You are able to update "Configuration" settings after importing a ThingTemplate but, I think, you can't update "Properties".
"Properties" values have to be set at Thing Level, the ThingTemplate only provide definitions (including default value).
"Configuration" values can be updated at ThingTemplate level in order to provide default values for Things that will extend it.
Hope it helps.