This module allows you to selectively disable regions on a variant-by-variant basis within Panels. It's somewhat of a replacement for the 'Disable Drupal blocks/regions" checkbox.
Blocktable allows you to embed all the blocks in a region into an HTML table. You create the table markup and place the blocks into it in any arrangement you want.
Page Preview is a low-impact alternative to Drupal's core node preview functionality.
This module re-implements the Preview area of the node edit form as an IFRAME that renders and displays the full page view of your edited content as the anonymous user would see it, including elements such as blocks that display as a reaction to the page context. The module also supports Page Manager (part of the Chaos Tools suite), meaning you should be able to preview nodes that are being rendered by Panels in full page form, as well.