Talk with your Sage Partner / Reseller.  They are there to answer just this exact type of question.

Documentation (including supported platforms): http://cdn.na.sage.com/docs/en/customer/100erp/Documentation.htm

SQL licenses are not included, and your data is more secure in SQL (compared with Providex). 

Writing raw data to Sage databases is always a very bad idea, since you're bypassing the Sage business logic.  While technically possible, don't do it.

Premium is great if the plan is more efficient reporting and analytics. ProvideX's SQL emulation is slower than native ProvideX file access. 

Perfect world would to retire WindX CS and invest in moving business logic to the SQL server in the form of functions and views.