@SophieBxnks Don't worry about the delay; it's never an issue.
The link you've sent me is throwing an error about the selected case no longer being available, and it looks like the site is assigning the default case for that build instead. That's a problem because there's no room for a disc drive, although the case is fine in general. So you can pick another case that does have room, or go with an external drive instead. Or you could contact Cyberpower and ask when the case might be available again.
The rest of the core components look great.
As for the monitor, mouse, and keyboard, I personally think it would be better to go shopping with your son and pick out these accessories. All three can be highly personal choices, and even a high quality option can happen to work badly for a particular person for one reason or another. For example, the mouse might not fit right in someone's hand, or the keyboard might be too "clicky" (or not clicky enough). The other option is to get a cheap mouse and keyboard and let your son pick out what he wants on his own at some later time.
The monitor in particular is almost impossible to choose for someone else. As an example, Dell makes high-quality monitors that many people like. But I would never want one just because of the way they look, and I've talked to other people who feel the same way. The best way to choose a monitor is to go into a store and just look at the screens on display, then make a list of what brands you like.
On the subject of the monitor you chose, it's fine for what it is, but it's in the lowest category in terms of image. TN panels are cheap with high refresh rates, great for competitive gamers or people who don't have a lot of money to spend. But their color panels are not great, and their viewing angles are limited. At the other end are IPS monitors, with brilliant colors, wide viewing angles, and typically lower refresh rates. The 144 Hz models can be quite expensive. In the middle are VA panels, with good colors and a lot of options in terms of refresh rate.
The other detail that matters is the resolution. A 27" monitor at 1920x1080 is going to look pixellated up close, but of course a 2560x1440 (QHD) or 3840x2160 (4k) monitor will be more expensive. Sims 4 would look great in QHD, and a 2060 Super could probably maintain somewhere close to 144 Hz, or maybe not quite that high. The refresh rate would be considerably lower in 4k. On the other hand, Sims 4 doesn't require fast reaction times, so many people would happily play on a 60 Hz monitor.
The reason I didn't bring all this up before is that you asked if the graphics card would work with a TV, so I thought that was your plan. I'm sorry, I should have asked, but monitors are a whole other subject that require their own discussion. Still, all specs aside, how a monitor looks is the most important factor. It's not quite as complicated as it seems though—all panels from a given manufacturer in a given category (IPS, VA, or TN) will look pretty much the same, aside from the resolution. So if you like the look of, say, one Samsung VA panel, you'll probably like the look of all Samsung VA panels equally well.
It should also be noted that Cyberpower's monitor prices are somewhat inflated, or at least they were the last time I checked. You'd probably do better ordering from Amazon or a local store.
P.S. You don't need to explain this whole discussion to your son if you don't want to. I help because I enjoy it, not for the appreciation, and there's little on this site that's more fun than picking out parts for a new computer. So however much you want to share with him is fine.
