have you checked this:

https://learn.microsoft.com/en-us/azure/databricks/archive/azure/synapse-polybase

tbh I do not use Databricks to load data into synapse. I write the data as parquet /delta lake on our data lake, and use ADF to copy to synapse if necessary. this goes pretty fast.

Another option is to use Synapse Serverless or External tables on the parquet files themselves.