Latest Roku Ultra vs my 2nd gen 4660X

My 4660 will do 4k HDR at 60fps but obviously not Dolby Vision or HDR10+.  Does the latest version also have a "passthrough" setting to allow the TV to do the upscaling instead of the Roku?  Has anyone compared the upscaling capabilities of your Roku vs your TV and if so, was there a visible difference? 

I am asking because I am getting ready to replace my 2017 Samsung 55" KS8000 (which is a 4k, 120hz TV) with a 65" something from one of the "big 3" i.e., LG, Sony or Samsung.  Leaning away from Samsung because it doesn't support Dolby Vision.