The power limit adjusted back up to 65w PL1/PL2 in the 2P4E configuration is enough to stop all frequency stutter in single-core tasks, and you can see there is a consistent cpu frequency maintained in Timespy. The power budget is thus 65w + 115w = 180w, very comfortably within the ability of the SlimQ 240w GAN brick.
Chef's kiss. That is a beautifully flat 5GHz CPU line, that will give you some excellent frame-time consistency.