[Build Help] Budget Ryzen Gaming(ish) Build for 15 Year Old Brother

I'm building this PC for my 15 year old brother, it will be his very first PC as he has had only laptops up until this point and is sick of them.

In terms of performance, he wants to be able to run CS:GO and some older AAA games (at least a couple of years old) without lag or huge frame-rate drops at medium or so settings (not sure how realistic this is at this budget but I'm trying to get him as close as I can).

My budget is AUD$1000 plus $50 for the mouse. The $1000 is very strict because its a birthday/christmas present from my parents and they won't budge on how much they want to spend and the $50 mouse is my separate present and is a little flexible but I'd rather keep it as close to that as possible. I'm open to other mouse options though.

I'm buying the parts only from places I can pick up from in NSW so that limits things a little too but also helps because I don't need to worry about postage.

PCPartPicker part list / Price breakdown by merchant

He needs WiFi as there is no cable into his room and I wanted to get an ac capable card so he has decent speeds so that's why I picked that WiFi card. It was the cheapest ac card I could find, I'm happy to take suggestions on other available ac WiFi options within the budget though.

He told me he wanted the cheapest case with a window so that's why I picked that case and he wanted an LED fan that isn't too noisy and that's why I picked that one.

I picked the mouse because he wants a gaming mouse with LED lighting and it was around my budget and seems fine but if there is a better option available with those features then I'm happy to change it.

I basically just want to make sure everything will work well together and that there aren't any major issues with any of the components before I make the leap and order all the parts.