Just upgraded from the old Flash Form Builder to the new one (full version), and have been re-building an old form from scratch. It has a Drop Down that uses the preset country list. The height of the Drop Down is only about half the height of all the other form elements and I can't see any way of making it match. Is it possible? It looks fairly untidy as it is.

Also, if I make all the form elements (and their names) the same as the old form, will I be able to continue to use the existing MySQL table on our server (which was created by the old Web Forms Builder) to hold the data?

Yes, you can continue to use MySQL with the new version. Just go to Settings > Saving Data to configure it.