The qt-creator will choose right compile option depend on your project is Debug or Release.
You can see compile output when compiling and you will find this:
Debug:
@cl -c -nologo -Zm200 -Zc:wchar_t- -Zi -MDd -GR -EHsc ....@
Release:
@cl -c -nologo -Zm200 -Zc:wchar_t- -O2 -MD -GR -EHsc ....@