There are a lot of variables to consider when answering your question, but here's what we do. Our WiFi Ranger can combine a WiFi signal and a cell phone signal to give us the best internet signal available.
If we have no WiFi signal at all, we can tell the WiFi Ranger to use only cellular data. If we have a strong WiFi signal, we can tell it to use only WiFi. If the WiFi is sketchy, for whatever reason, we can tell it to use 25% WiFi and 75% cellular, or any other ratio that works. Of course, if you don't have a WiFi or cellular signal, boosters won't help. You can't boost a signal that's not there.
If you can get the antennas above the RV's roof, you will realize a significant improvement in range, especially in fringe areas. Our daughter lives a quarter of a mile from us, and our devices cannot even "see" her home WiFi network when we're standing outside. However, when I raise our RV's external antennas, and connect our devices with the WiFi Ranger, we can easily connect with her network.
Kev