According to industry observers, it will be the redesigned iMac and not the MacBook Pro 16 that will truly be able to unlock the full potential of an expected M1X Apple Silicon. Even with an updated cooling solution, thermal restrictions will prevent the MacBook Pro 16 from hitting the performance heights of a larger M1X iMac device.
https://www.notebookcheck.net/Redesigned-iMac-with-M1X-chip-will-offer-the-true-pro-levels-of-performance-that-can-be-expected-from-the-next-generation-Apple-Silicon.528398.0.html