As for the seed phrases it's 2048 words with 12 to 24 total in random order so you do the math. But as far as passphrases, they still work too. They are the 12th word or sometimes 24th word even. Also if random generated you are measuring bits not length. So 16 random numbers, special characters, letters, and symbols are pretty much random too. Some people reduce it down to a very large number, that would take hundreds of millions of years to crack. It all kind of depends on how much you care.