I would especially not leave the ATV set to DV or HDR if using an OLED TV. Forcing a higher peak brightness on content made not to go that bright and on screen savers which are supposed to help preserve your display will ultimately shorten the life of your display. OLED elements degrade with use and they degrade even faster with running them brighter. If you care about longevity of your OLED set then save the DV and HDR brightness for content that is meant to be seen that way.
I would especially not leave the ATV set to DV or HDR if using an OLED TV. Forcing a higher peak brightness on content made not to go that bright and on screen savers which are supposed to help preserve your display will ultimately shorten the life of your display. OLED elements degrade with use and they degrade even faster with running them brighter. If you care about longevity of your OLED set then save the DV and HDR brightness for content that is meant to be seen that way.