Hi @Anonymous ,
First answer the side question, currently Flow supports Word Template but we are unable to use Excel template.
If you want a similar feature to be supported by MS Flow, please consider submitting your suggestion on the ideas forum:
https://powerusers.microsoft.com/t5/Flow-Ideas/idb-p/FlowIdeas
In addition, according to your description, Flow needs to monitor the changes of data in the Excel table. Currently, this is also not supported, and no similar trigger is available.
You could consider using SharePoint List, so you can use the actions contained in the SharePoint connector to try to achieve your needs.
Best Regards,