Find the option needed by the Compiler; and then ask here how to add it to CB.
I will now read the code part of your post.
Edit: NOTE some of the MinGW GCC do NOT have an option instead they have a different toolchain for 64 or 32 bit.
The name of "x86_64-w64-mingw32-g++.exe" implies this to be true for the MinGW compiler you are using.
Ask your question at the site where you got the compiler to get the real true correct answer.
Edit2: If you installed two MinGW GCC installations you will likely have to use either two CB Profiles or use two CB Compiler setups under a single CB profile. I find using two CB Profiles to be better if you plan to share your CB projects with anyone else.
But, using to CB Compiler setups one for 32 bit and another or 64 bit is easier; if you do that method I suggest copying the CB GCC compiler setup to make the copy be "gcc32" for the 32 bit compiler.
Tim S.