The author says that you don't need to choose between 4K and 120Hz, because there are "reasonably priced" monitors on the market that have both. But their recommended monitor ($900) seems a lot more expensive than a 4K 60Hz monitor (which is around $300-$400 when I search on Amazon).

The author also says (they think) that you need the discrete graphics card in a MacBook to take advantage of a 120 Hz display, and that the integrated Intel Iris graphics won't do.

I was actually shopping around for a new MacBook earlier today, and noticed that the 13" MacBook Pros only come with integrated GPUs, and you have to get the 16" MBP if you want discrete graphics. So if you like the portability that a 13" laptop has, this might not be a good tradeoff (not to mention that the 16" one costs $400 to $800 more than the top-spec 13" one).

I totally agree with the stuff they say about rendering fonts on 4k screens, but I don't think I'd be willing to take the hit in portability, or shell out an extra $700+, to get 120 Hz.