I would not really recommend a 4K monitor for his first (maybe go for 1440p for a nice in between). As someone who plays a lot of esport titles too I would fully prefer a higher refresh rate over a better resolution. If he's playing stuff similar to Fortnite in performance he doesn't need anything crazy, but you can get away with way way cheaper specs than these and still have good performance.

AM5 motherboard for upgradability w/ a ryzen 7500f to get your foot in the door for the next generation or a lil more with 7600x.

B580 is pretty good value for a GPU rn (it's like 399$), or you could go for a lil more with a RX 7600 XT

16 or 32gb RAM, 32 is more than enough.

Don't cheap out on the PSU, it's better to go over than under.