RUT241 has only one antenna dedicated for WiFi. Using different orientation might be a suitable option to try with more antennas, to try covering more areas in places further from the router, but the general suggestion is to leave the antenna in a vertical position.
The remaining antennas are for the mobile connectivity. They serve different purposes, Main one being used for mobile reception and transmission and Aux being used for reception, to implement MISO (Multiple Input Single Output), to improve signal reception.