1) How do you add photos/captions to a converted gallery from NGG ?
A NextGEN-sourced WP-Juicebox gallery is not 'converted'. Juicebox creates the gallery live from the NextGEN data at the time the gallery is displayed. Therefore, just add images and/or captions to the NextGEN gallery that WP-Juicebox uses and the changes will be reflected in the Juicebox gallery the next time the gallery is displayed.
2) Currently the image title + caption is both showing on the WP-Juicebox gallery; how do I just show the caption?
Either clear the 'Alt & Title Text' fields in your NextGEN gallery or modify WP-Juicebox as follows.
(1) Open the 'wp-juicebox/config.php' file in a plain text editor.
(2) Change line 101 from:
$title_text = $new_dom_doc->createCDATASection($attachment->alttext);
$title_text = $new_dom_doc->createCDATASection('');
(3) Save the change and re-upload the file to its original location on your web server.
Please note that the line number refers to WP-Juicebox v1.2.0.
3) How would I move the thumbnails from the bottom section to say the left or right, or even top?
(1) Upgrade WP-Juicebox from Juicebox-Lite (which it comes bundled with) to Juicebox-Pro by following the instructions here.
(2) Use the thumbsPosition configuration option in the 'Pro Options' text area of your gallery's settings window, e.g.
A description of the thumbsPosition configuration option can be found in the Thumbnail Options section of the Config Options page.