Those 120mm rads just run hot. I just removed one and used a 17 dollar air cooler with a 7c drop in temp on a 6 core ryzen. 82c was its max temp with cinebench 23. 30 min soak on a 120 aio.75c with air and once the load was gone, it drops to 37c super quick. You could try a higher CFM fan on the rad itself and keep your pump rpm at 60 percent at idle to 100 percent at 70c.
Its the peaks of over 90c + shouldn't happen on a aio.