It seems to be doing good, coming from the old Corsair H100i Pro 240, with the H100 my idle temp was around 45c, gaming around 66-70c depending on game and under full all core load it hit 90c Fast!
With the 280 i get 39-41c idle, ran the Division 2 for a few hours lastnight, solid 63c and under full all core load it topped at 86c. It runs a bit quieter too and i have not touched a thing in the bios for the header its using, fully running at defaults at present, so RPM in HWINFO showed around 1000rpm give or take a few while idle.
I used Thermal Grizzley Kryonaught with both coolers so same brand paste used on both.