If the “M1X”, as rumoured, has something like double the number of CPU and GPU cores then it should be significantly faster on some workloads, particularly video, audio, image processing apps that are optimised for multi-threading & GPU-based comouting... at the expense of more power consumption & needing a larger laptop, or desktop, housing. C.f. the also-rumoured “M2” which will have new core designs and maybe a tweaked production process but will likely start out as a low-power configuration for MacBook Airs and iPads. The M1X is likely to be considerably faster than the M2 for many multithreaded “pro” applications. In time, there may be a “M2X” with more cores.
More I/O, more RAM, more display support will likely also be needed with the -X processors, of course, but while an M1 extended with 32-64GB RAM and support for 3-4 displays could potentially match current Intel MBPs and iMacs, it wouldn’t be much of an upgrade.