If you want to use Google Sheets as 'live' SQL data sources consider to use a BI tool that has a DuckDB connector. DuckDB has gsheets extension (https://duckdb.org/community_extensions/extensions/gsheets.h...) and it works like a charm.

In particular, Metabase and Superset can be deployed with DuckDB support. You mentioned customer facing dashboards, note that Metabase embedded is not free. Just to say, our SeekTable also has DuckDB connector (and can be used as an embedded BI).