Unfortunately the Jupiter Saturn conjunction will not be directly overhead...but it's important to take the pictures as early as possible, before they get even closer to the horizon and MUCH more air comes between us and them.There is more than gear and settings to shooting the moon and planets. Another common and very impactful source of blur are disturbances in the atmosphere. Especially if the object you are shooting isn't right above you, you're looking through a lot of air that can wobble and distort the image in the process. It what maker's stars twinkle. If you observe the moon through LiveView it will be easy to judge how the 'seeing' is in a given night.
Ideally, you get lucky and just image on a very still night and wait until the moon / planet has risen sufficiently far above the horizon. Another strategy to combat this has already been described.
Take lots of pictures and let software Analyse them to combine and stack the sharpest sections of them all into one image with less noise and less impact from the atmosphere. The technique is called lucky imaging and is usually applied by taking an uncompressed video with a special type of camera.
I think on an R6 / R5 you are better off just using the electronic shutter 20 FPS burst mode until the buffer is full. That saves you from any forms of compression, or overheating and requires a little less processing power on the computer compared to the RAW video options.
Free software that does this is Autostakkert or Registax, for example.
On the other hand later at night is likely to be better because it's cooler and less thermal convection.
The idea of just filling the buffer in electronic shutter mode sounds promising, because any one shot is liable to be blurry thanks to our atmosphere, but there are occasional instants of clarity. (It's going to take a lot of work to step through and magnify each shot to look for the best ones, though!) I generally keep almost everything I shoot but in this case I'll be trashcanning a lot of shots; I do NOT want this to become the first >100GB shooting session on my NAS.