You are configuring Azure Synapse Analytics pools to support an Azure Active Directory group (Group2) with the requirement to 'Execute complex queries with multiple joins against relational data…

Apache Spark pools are primarily for big data processing, data engineering, and machine learning, not specifically for relational data warehousing with complex SQL joins and PolyBase export.

Dedicated SQL pools in Azure Synapse Analytics are provisioned, enterprise-grade data warehouses specifically optimized for intensive analytical workloads, including complex queries with multiple joins against large relational datasets. They provide the necessary performance and capabilities, including integration with PolyBase for high-throughput data loading and exporting.

Serverless SQL pools are designed for ad-hoc querying of data in data lakes without provisioning resources, making them less suitable for the sustained performance and dedicated resources required for complex, high-volume relational queries as implied by "multiple joins against relational data" and PolyBase export.