The pins on the module are 1.8V. The pinmux and design guide talk about the module itself.
The devkit board contains a level shifter, so if you access the SPI bus on the J41 header, that level shifter has been applied.
If you need to build your own level shifter, I recommend a TXB0104 translator chip from Texas Instruments, and you can reconstruct 1.8V from a 3.3V power source with a simple low-current LDO like the MIC5365-1.8 from Microchip Technology. Add two capacitors (the MIC and the TXB can share 1uF ceramic decoupling capacitors) and you’re good to go! The TXB0104 is very simple to use. (SparkFun also has one available on a board for $4, although without the voltage regulators: https://www.sparkfun.com/products/11771 )