As others have mentioned, the liquid freezer ii 280 is a great AIO, and they also mentioned the fat radiator, but I just wanted to point to that fact and let you know to make sure you have room for that thicker radiator before buying it. It will make the fans mount lower in the system (closer to the motherboard) and not every case has room for that. In some cases you can lower the motherboard, but not all of them. Also, I wouldn't put that AIO on the front as it will then put that hot air into the system, raising the ambient temperatures of your GPU, VRM, memory, etc. It's often not a deal-breaker to do that, but if your main use is putting the GPU under load, you want fresh air going to it as much as possible, so it's ideal to have that radiator as an exhaust in the top.
That said, the approach you've taken above seems to be good. I was going to suggest you can probably get away with an increase in PL1 and then do a slight voltage offset and gain performance without losing much in terms of temperatures, but it looks like you're there.
The Intel XTU app is helpful for doing some tuning within Windows, but I prefer to do my tuning in the BIOS. Sometimes it's helpful to find what works with the app then go back and try to run it in BIOS once you have those numbers figured out. the XTU settings only stick if you're running that at start-up. It would then apply those settings every time you boot the PC. This is normally fine, but I always prefer less background apps whenever possible, and if it's actually stable, it'll be stable if applied from BIOS.
