It already exists? You can buy ARM Windows devices right now. I'm typing this on one. The x86/x64 emulator is pretty good but performance is limited by the slower CPUs.
We can already use the Windows x86/x64 emulator. Unless you have specifics that Snapdragon X Elite performs worse under it than current chips we can expect about 60% the performance. Rosetta 2 is about 75%. Based on Qualcomm's Geekbench 6 numbers it'll have about the same x86/x64 performance as the M1.
It already exists? You can buy ARM Windows devices right now. I'm typing this on one. The x86/x64 emulator is pretty good but performance is limited by the slower CPUs.