Is this a good high-end PC build for gaming and video editing?

The RTX 5080 is a capable choice, but it can be poor value depending on its price. A Radeon 9070 XT or a less expensive NVIDIA card could offer better price-to-performance, while NVIDIA may still be preferable if your editing software benefits from CUDA or specific encoder features. Choose based on the games and editing applications you actually use.

I would increase storage to at least 2TB, and possibly 4TB if you keep lots of game installations and video footage. PCIe 4.0 is already plenty fast for gaming and most editing; PCIe 5.0 usually adds cost without a noticeable improvement. A quality, reliable SSD matters more than chasing the highest advertised transfer speed.

The 360mm cooler is only really necessary for a high-core-count Ryzen 9. If you choose a 9800X3D, a good dual-tower air cooler should be sufficient, quieter, and simpler. An 850W or 1000W ATX 3.1 power supply from a reputable manufacturer should work depending on the final GPU, and the X870 board is fine as long as it has the features and connectivity you need.

For the monitor, choose based on resolution and refresh rate rather than brand alone. A 27-inch 1440p OLED around 240Hz is a strong choice for competitive gaming, while a 32-inch 4K OLED around 240Hz is better for sharper visuals and high-end single-player games. Check whether your preferred model has good text clarity, warranty coverage, and burn-in protection before buying.