You just have to make sure that any new project you start has new audio files saved in an audio folder in the correct project folder.
When I start new projects in Nuendo I choose the template in the HUB and it will ask me to specify a folder and at that stage I either create a new folder or choose one I created earlier - but it has to be a folder that’s different from the templates folder.
That’s the one thing you need to keep track of to avoid having new audio saved in your template folder.
My template only contains the names of the tracks there is no audio data
I have already created my next project using the template as the basis and when data was injected the project got saved under a different name.
If you have audio files in your Audio Pool, they will get saved with your template as well.
If you don’t need any audio files in your template(s), just remember to empty it out before saving the template.
No data on tracks is NOT enough. You might still have audio files in your pool. If you later use that template for a new song and do a “remove unused files>delete” then you risk deleting audio used in other projects by mistake. Not fun.