Is it possible to import product data from excel to Shopware 6?
Is there an API for that or some plugin ?
If not, can this be achieve through direct insertions into tables ?
You can use the Import/Export module in the admin to import csv files: https://docs.shopware.com/en/shopware-en/settings/importexport
Hint: I recommend you to not use Excel, as they work with their own format which can cause issues during an import.
Note that there are many bugs in the import/export, e.g. sales channel column always fails to work.
We are aware of the issue. The ticket will be scheduled in one of the next releases. 