Both the clockwork A-0602 and A-0604 have a cortex A72, which is what the Raspberry Pi 4 has; just the raspberry Pi is clocked at 1.5GHz and the Clockwork Pi is clocked at 1.8GHz.
The clockwork pi also has an arguably more powerful quad core Mali T864/T860 MP4 GPU, compared to the raspberry pi’s videocore VI. From memory the die is smaller on the t864 (28nm) compared to the videocore VI’s (40nm) which should in theory be cooler.
I may have overlooked something, but statistic wise, the Clockwork Pi high end offering seems to be the better choice, and comparable in price.
I’m not sure exactly how having a fan would immediately mean that a raspberry Pi 4 will work, seeing as due to its configuration of overheating components, it would need a specifically made/targetted heat sink that conducts heat away from the hot spots.
I’d be weary of anyone who says that the raspberry Pi 4 would be compatible, without any anecdotal evidence. Currently, all evidence points to it not being compatible.