Can someone please help me instead of just pointing me to the manuals?

No such luck :)

There are areas of improvement that I see, one being an effective node title :) How do I compose an effective node title?

You probably had a tough time coming up with one, because your code is not self-contained, and you're asking more than one question , for improving on that :) see How do I post a question effectively?

I imagine, an effective title might be "Creating generic DBIx... model template" or "DBIx... introspection" or ...

The problem is, what if I want to display the results of a different DB? Seems that I should be able to use the same template... maybe I'm just not groking the model.

From your template/description, I can deduce, that resultset is basically this data structure ( an AoH, array of hashrefs)

[
  { username => 'username1', password => 'password1', ...},
  { username => 'username2', password => 'password2', ...},
  ...
],
[download]

So to make your template generic, you would use the Template equivalent of keys, which is keys so

<table>
[% IF hash = resultset.first %]
  <tr>
    [% FOREACH key IN hash.keys.sort %]
       <th>[% key %]</th>
    [% END %]
  </tr>
[% END %]
[% FOREACH hash IN resultset %]
  <tr>
    [% FOREACH key IN hash.keys.sort %]
       <td>[% hash.$key %]</td>
    [% END %]
  </tr>
[% END %]
</table>
[download]

->all probably returns different data structures in different context, see Tutorials: Context in Perl: Context tutorial, about context, and also see the related DBIx documentation :)

For data structure info see perldata and the tuts it references, and same for Template :)

There are other ways to a generic template, but I can't help you with that :)