With a intel Q6600 (a 2007 CPU), 4Gb of RAM and a Radeon RX460 2G, windows 10.
Playing in real time in the Preview Window best quality (Total) a 1920X1080X32 video with color correction and 2 GPU acelerated filters with a maximun CPU charge 50%. Not a frame drop. Obiously all the work is done by the GPU, but let me tell you that Davinci Resolve uses a SQL database that install in your system and, in my case, draw nearly my 40% of my CPU power just to run.
I want the users to get the whole picture of this, because some people are posting problems with 4K rare codecs and configuration problems in their systems and some newbies are getting a terrible impresion of this EXCELENT piece of sotware.
So do not get confused by some "users" that, instead of using like all of us, videos of their phones, cameras, normal resolutions etc.. are, strangely, using always rare codecs, rare source videos and configurations that always gives them problems that YOU ARE NOT GOING TO HAVE the 99% of the time.
Try vegas in an old computer and compare it with resolve or some bloated adobe software and you will see the level of optimization.