Encfs is pretty opaque -- afaik modifying a file will at least change an entire block, possibly the entire file. Two identical files will look completely different (per file IVs) -- so no deduplicaton is possible.
But adding and removing files works as expected, so adding a few files to the encfs system, should translate to the same number of files added to the underlying folder.
EncFS allows to deactivate some of these features at the price of reduced security. The EncFS manpage [1] has a good explanation of all the tunables. If you want to use Boxcryptor, you're even advised to deactivate most of these features [2].
But adding and removing files works as expected, so adding a few files to the encfs system, should translate to the same number of files added to the underlying folder.