With deep it scans all the texture folders in all your runtimes. That might take a while when you have a large (set of) runtime(s).

Search first tries to be intelligent and queries first the current folder, the root textures and some other locations. Then it parses the pathname and tries various mutation. Then it starts the full search. If it locates a texture, it then adds that folder to the set of locations to search in before it does the full search - finding the other textures with the same incorrect reference in that folder.

Settting it to shallow eliminates the full search. Setting it to narrow does not do any seach at all.