When you experience the slower upload throughput on WiFi , how close are you to the AP?
In your region, it is common for many APs to limit their transmit power to around 600mW, while many client devices will limit themselves to the 100-200 mW range, thus uploads over distance will often be a bit lower, as they are more likely to have frame errors with distance.
Another thing to test is enabling or disabling settings such as MU-MIMO, while it s uncommon for modern devices to have issues with it, some older devices may experience a slowdown when it is enabled. That setting can be found in the router page, advanced > Advanced Setup > Wireless Settings> [Enable MU-MIMO] checkbox.
When troubleshooting speed issues, also try to do the WiFi testing when about 2 meters or so from the router.
Another thing to test for, is the region listed in the WiFi setup page ( Router page > Basic tab> Wireless ). If the wrong region is listed, then make sure you are not using a channel that i not allowed for your region, also avoid channel 46 and 48 if you can, or any channels encompassing that segment of spectrum 5230MHz and 5240MHz. WiFi routers will limit-transmit power based on the most restrictive channel in the spectrum being used, thus those 2 channels in South Korea can be quite limiting.
If a setting change doesn't correct an issue, then return it to how it was previously set.
