Which AF Assist Beam is used with the EOS RP when a speedlite is used. The speedlite sometimes fires what I presume is an AF Assist Beam. Then other times the camera body fires its own AF assist beam. I know that infrared AF Assist won't work on mirrorless. But what is causing both speedlites to act like this. The EL-1 nor the 470EX-AI act this way on my DSLR bodies 5D Mark IV and my old 40D.
The assist beam that is fired depends on how your camera is set and the flash attached. To check that press the Menu button and go to the eighth page under the red camera tab and select AF-Assist Beam Firing. When that is set to Enable the EOS RP will use the assist beam built into the camera. If the camera is in either P, Tv, Av, or M photo mode you will have an additional option in that list for LED. When the assist beam setting is set the camera will use the assist beam from the attached flash. One thing to note with that is the flash assist beam will only fire if it has an LED assist beam.
If you want to reference the manual for that information it is on page 201. If you need a copy of the manual it is available HERE. Once you are on the web page click on the gray Manuals button and the one to reference is named EOS RP Advanced User Guide.
The manual for the EL-1 speedlite mentions this for the AF Assist Beam projection method. I would like to only use the speedlite AF Assist Beam (Intermittent Flash Firing Method). Would setting LED Firing to "Disable" allow the speedlite to project an AF Assist Beam. The manual for the 470EX-AI doesn't say how an AF Assist Beam will work with the EOS R series cameras. But the 470EX-AI acts in a similar manner to the EL-1.