From what I'm reading here in the forums and the posts on WC, the emulation will not be compatible with current hardware, but I can't say for sure for the SD820 on the Elite X3 as well as the Idol 4S. The last flagship Lumias, both running SD810 and SD808 respectively, will unfortunately not be able to run the emulator at all.
But from what I read, Microsoft had made some agreement with Qualcom to produce a customized SD830 which will enable the processor to run x86 apps via emulation, so this removes the need for a dedicated x86 processors like the Atom processors by Intel, making ARM chips more than sufficient.
But alas, I may have read the article wrongly. Too long for me to remember everything tho.