https://bugs.winehq.org/show_bug.cgi?id=57859
--- Comment #76 from Shmerl shtetldik@gmail.com --- (In reply to CWB from comment #75)
Am I understanding correctly that `WINEARCH=wow64 wine somewin32.exe` will use the new wow64 mode, while anything else will use the old one? Does it matter how the prefix was initially created? (Does it work in an existing win64 prefix? Does it work in an existing win32 prefix? Is there such a thing as a wow64 prefix?)
Not sure if there is a flavor of wow64 prefix, but to your other question - yes, from my testing if you run a 32-bit program in a 64-bit prefix that was created in the past (or now), it will use 32-bit libraries proper using the old style wow64, but if you set WINEARCH=wow64, it will use 64-bit libraries in that special thunking mode (new style of wow64).
I.e. basically you can now do both with forcing the new mode with a variable. I don't use 32-bit prefixes anymore since there is really no point in them so can't say what will happen there, but wow64 is irrelevant for them anyway.