Well you're #2 request should be simple. Any CMS should be capable of doing that even if you have to write a little jQuery so that links under a specific criteria (a img, or a.some-class, etc...) are handled by a lightbox extension or something like that. So in that case you're link is pointed at the big picture but when you click the link, jQuery + a Lightbox plugin take over and instead of completing the request, they create a lightbox to display the image. If you used a special class to activate the jQuery you could make any page a "Portfolio" page by linking thumbnails to their larger counterparts and giving the links a class of "portfolio" or whatever you decide to use as the trigger.
For your #1 request you can also use pretty much any modern CMS. Although you've indicated that you want to try something different I would say Drupal 7 (which is a different Drupal than earlier versions) can definitely pull this off with the help of the Media Gallery Module. You'd need Media Gallery, Media API + File Entity and then to really make it shine, add the Plupload integration module so you can drag-n-drop files into the upload field (you can grab multiple files, drop them in the upload field and upload them all at once). You can have as many galleries as you like and rearrange the order of the images by dragging them around (a bit like Facebook Galleries). You can create as many portfolio sets and arrange them in a grid.