I think someone mentioned the Strix-i's VRM throttles around 150W.
The ASRock Fatal1ty ITX has good VRMs but unfortunately they're BIOS locked at 200W (no problems for the VRM).
If I'd weigh the differences,
-Easier to find a closer fittint monoblock (Ek STRIX-I Z270 block doesn't touch the inductors unfortunately)
-No idea how the fan headers are set up, potentially they're all DC/PWM switchable
-Really bad Realtek WiFi chipset
-Phenomenal POST times, typically 7-7.7 seconds with heavily overclocked RAMs with fastboot/windows 10 hybrid shutdown disabled (dGPU, I haven't tried iGPU + JEDEC-2133)
-Pretty sparse BIOS
>vCore in 5mV increments (fixed)
>vCore in 10mV increments (offsets)
>VccIO in 5mV increments
>VccSA in 50mV increments
(I hope the BIOS engineers aren't drunk...)
-1X DC/PWM fan header (CPU OPT)
-2X PWM fan header (CPU/CHA)
-2 Lane Thunderbolt
(it might make a decent lan party box with an eGPU GTX 1060)
-USB-PD Charging up to 36W
-AC8265 Intel WiFi chipset
You might be kneecapped with the strix-i VRMs, but it has potentially a better DC mode fan control across all headers and potentially abit better granularity with the BIOS.
But VRMs, connectivity (superior WiFi chipset) goes to the fatal1ty, better IO (unless raid 0 M.2 is your pick) goes to fatal1ty.
If there was a Maximus X Impact that might be a clear winner. (Asus@Raja - No impact planned for this gen). Neither of these boards are perfect. If you got the Fatal1ty, you need to make sure your planned loop has a low dependency on DC fan headers.