The plugin is compatible with Aelia Currency Switcher plugin. This lets you see the cost of your goods correctly updated based on the selected currency.
No, reports can be general or by products or categories. Yet, you can further filter the reports by tag, by simply clicking on the tag name in the report.
Make sure you’ve enabled the Tag column in the reports from YITH > Cost of Goods > General:
Then, you can filter any report by clicking on the tag name: