You need to follow this documentation here to create custom template, but to do that you would need to clone the current data stream template, so I don't think you can't do that before creating the data streams.
Depending on the integration you will need to create a custom template for every dataset that the integration have, which is a lot of work.
I opened an issue for a feature request to simplify this process and it seems that Elastic is working on it.
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