Tommy,
The form Data model is meant to work with Adaptive Forms authoring.
Please see [1].
For HTML5 forms, most features work the same as they do in PDF. Here is a list of the differences at [2].
If you setup an OLEDB connection in your XDP to pass data into your form, I believe the DB connection should still work server side. I'm not sure if the connection is supported on the client.

I have not tried this myself in HTML5 forms, but most of the XFA constructs [2] are still supported server side if I am not mistaken.
[1] Adobe Experience Manager Help | AEM Forms Data Integration
[2] Adobe Experience Manager Help | Feature differentiation between HTML5 forms and PDF forms