I don't know specifically about the parks you're looking at, but lot rent almost always includes the real estate taxes. After all, you as the resident don't own the property; the company that owns the park does. So it pays the property tax on the land it owns. It passes those costs on to you as a portion of the lot rent. There may be a separate annual tax you'd pay on the structure--just like the personal property tax that some states charge on automobiles. But--to answer your question--you shouldn't be receiving a bill from the state for property tax on property owned by the park owners.
The variations I've seen in lot rents is attributable to other factors. For example, some parks have swimming pools. Others don't. Some have a guard at the front gate. Others don't. Some have a clubhouse. Others don't. Some have tennis courts. Others don't. Some have paid on-site management. Others don't. And so on. You take one park with a lot of those amenities and another with few or none, and you'll get a wide variation in the lot rents.