The build is upgraded from the previous 2017 8700K build.
The minor changes are the 9900K CPU, Maximus XI Apex Motherboard, Trident Z 4000 ram
The major changes are the monitors, PG27UQ for HDR, PG35VQ for 21:9 ultra gaming, while Zowie XL2740 remains the Esport monitor.
Other details I might add later:
The 5-year-old Corsair H110 still goes strong. It has the same performance as the new Corsair Pro version, I guess the radiator quality is superb. Plus Noctua is doing the major work.
2X2TB 970 EVO Plus M.2 Storage for faster loading time.
No SS3 support for Apex motherboard, but Maximus Gene has SS3, which is unexpected.
9900K 1.39V 5.1GHz stable but the temps are quite high, reach 80C frequently. After stability test, I can see 9900K temp is higher and it passed both Prime95 and real bench. 115C is the max.
Old bios for Apex is more friendly for low-latency overclocking, I managed to get C14 4266 1.8V stable.