Your understanding is correct. These preview and test folders that are created locally are related to the test and preview versions of the survey respectively. If these folders are removed, they will be recreated as needed.
The names of these folders have changed a bit to try to make things clearer in this version. In addition, we used to run a copy of Apache in the background to serve these pages, but Lighthouse Studio now has its own built in webserver to accomplish this function, which makes it a bit less of a headache for some IT departments trying to get Lighthouse Studio to work in their locked down enterprise environments.