expectedly , it's still throttling with my 90w PSU. With ThrottleStop I also noticed Radeon throttling at +84C. It seems like XPS thermal design isn't that good to handle discrete GPU's
ThrottleStop OFF
GPU: +80C, core Clk: 675, Mem Clk: 796
CPU: +62C, Multi: x10
ThrottleStop ON
GPU: +74C/+84C, core Clk: 300/675, Mem Clk: 499/796
CPU: +77C, Multi: x20