Number of thumbnails shown on folders

When I have a lister displayed in thumbnails mode containing pictures (or PDFs) and subfolders with the same kind of files, these subfolders are displayed as thumbnails divided in four parts showing thumbnails of the four first files (or less if they contain less than four files) in them.

Is it possible to change this division number ? I'd like the folders to have only the first file (so the thumbnail is bigger and there is no empty space if it contains only 1-3 files) in them displayed, but can't find an option for this (I'm not even sure if DOpus has some control on this behaviour or if it's handled by Explorer).

Second question (I can't find a "edit" button to add it to my message ; is it normal ?) : is it possible to remove the border around the thumbnails, in order to make them look like image-icons ?

Don't think you can change either of these at the moment.

(Plugins can set a flag to say whether their thumbnails should have borders or not, but you can't turn them off in general. e.g. There's no border around text-file thumbnails.)