I served on FF (Knox) and FFG (Perry) class frigates. The frigate is your entry level ocean going vessel. LCS’s are closer to corvettes, they would never be confused with a frigate.
This is where things get confusing. Some Navy’s use the term “frigate” for a coastal vessel. The USN used to use the term “Destroyer Escort” for ocean-going escort ships, but changed to “frigate” during the Knox-class (or possibly the earlier Brooke-class). I believe that the Knox was originally designated hull “DE-1052”.