The Raspberry Pi 4 has worse overclocking potential than the Compute Module 4 and Pi 400
The Raspberry Pi Foundation currently sells three versions of the Raspberry Pi 4: the Model B edition, the Compute Module 4 (CM4) and the recently-announced Pi 400. The Foundation aims the three machines at different audiences, but it turns out that they are not quite the same device in three flavours. Instead, the Foundation has equipped the CM4 and Pi 400 with a newer chipset than it uses in the Model B. Specifically, the latter has a Broadcom 2711ZPKFSB06B0T, while the two other devices have the newer Broadcom 2711ZPKFSB06C0T.
According to Hackaday, the change in chipset has given the CM4 and Pi 400 a few advantages over the Model B. On the one hand, the Broadcom 2711ZPKFSB06C0T runs up to 10 °C cooler at 1.5 GHz than its predecessor, a difference that may explain why the Foundation has clocked the Pi 400 at 300 MHz higher than the CM4 and Model B.
On the other hand, the CM4 and Pi 400 can be overclocked higher than the Model B at the same temperatures. Hackaday notes that the Pi 400 can maintain 2.15 GHz, for example, which is a 43% overclock on the stock clock speed of the Model B. The CM4 can match the temperatures of a stock Model B while running at 1.8 GHz, too.
All three devices can reach 2.0 GHz with an aluminium heatsink, though. However, the Pi 400 comes with one built-in, handing it an advantage over the CM4 and Model B, unless you have one to hand for the latter two. If you would like to read more about how to overclock your Raspberry Pi, then the Raspberry Pi Foundation has published documentation on doing so. Similarly, websites like Tom's Hardware have more user-friendly guides on overclocking any Raspberry Pi.