Yes, foldable. The “V symbol” should be customizable with magit-section-visibility-indicator (I see “…” at the end of the section title on my end).
If you press number 1, 2, 3, etc. you can control the visibility. So an alternative might be to display the backlinks buffer with level 2, instead of the “empty-string” solution above. This way, you can start the side-buffer with the detail folded – I think you can use the org-roam-mode-hook and call command magit-section-show-level-2.
I do not know why you cannot jump to the linked note in the backlink buffer, though… I cannot click on it (not a problem for me), but RET just works…