The only effect using DataAssist will have on the registration form is the Dreamweaver Check New User Name behavior, but there is a work around.
The check New user Name behavior is triggered by the MM_insert hidden form element:
<input type="hidden" name="MM_insert" value="WAATKRegistrationForm">
when you remove the Dreamweaver insert Record behavior, this hidden form element will be deleted too. You can manually add it back in.
For more details, see the Introduction to SecurityAssist -> Modifying registration tutorial in the solution recipe section of the Security Assist support page: