You have the ability to specify whether a particular column is editable by
determining how it is bound. Bound fields = not editable. Templated fields =
editable. You specify the item template and the edit template. This gives you
the option of making some fields drop down lists.

If you want to do this with the designer. Turn off auto gen of columns. Then
create each column as a bound column. If you drag a data table onto a form,
this is what you get for most items (bit fields will be a checkbox). Change
the columns you wish to edit to Template Columns. They will default to
textboxes. You can change this if you wish to bind to a list of items, like a
type table. There are plenty of tutorials for this on the web.