The 12" Dob will capture far greater resolution than the small refractor, but without tracking it will be harder. However, it is certainly possible to get very good images with an untracked Dob using a large sensor camera and let the planet drift across the sensor, for that the Uranus-C or ASI585MC would be the best, however the ASI678MC might also be an option.
Have a look at the Planetary AP FAQ here for more tips.
https://www.cloudynights.com/topic/8...-january-2023/
Andrew