What has changed from private preview to limited public preview in regard to data flows?

You won’t need to bring your own Azure Databricks clusters anymore.

Cluster construction and dismantling will be handled by Data Factory.

Delimited text and Apache Parquet files are segregated from blob datasets and Azure Data Lake Storage Gen2 datasets.

You may still store those files in Data Lake Storage Gen2 and Blob storage. For those storage engines, use the relevant connected service.