The question for us is the PEGA hosting (source) database and the Target database for export be of different types?
Yes, they can be different. The source is picked up based on the Data-Admin-DB-Table associated with the class on which the extract rule is defined. The target needs to be explicitly specified in the extract rule.
EG Source being DB2 and target being SQLServer?
Yes, definitely supported. Please check the platform support guide of the Pega platform for the versions of these two DB platforms that we support.
Are the DDLs generated from the BIX interface take care of SQLServer Target?
Yes, MS SQL Server is supported as long as the version of MS SQL Server is what is mentioned in our platform support guide for the Pega platform. The DDL is always generated based on the database vendor on the target specified in the extract rule.