I was very confused by both of libmono-2.0-x86_64.dll libmono-2.0-x86.dll MonoPosixHelper-x86_64.dll MonoPosixHelper-x86.dll in c:/windows/mono/mono-2.0/bin/
In fact libmono-2.0-x86_64.dll MonoPosixHelper-x86_64.dll are never used, at the moment.
Correct. Alexandre insisted we include 64-bit builds anyway. In theory, they would work if Wine had everything required.