Software Deployment

is this achievableIf you mean in one MSI, then no, it's not. You can obviously "package" both MSIs into a self-extracting EXE in which there is logic to detect the "bitness" of the OS and extract and execute the relevant MSI, though.

you could make the whole package 64bit(with the "Platform" Flag in the Summary Info), so it has access to both the 32 and the 64 bit folder structure.
then place the components in the directories you like.
the most easy and clean way would be IMHO to create an INSTALLDIR32 and INSTALLDIR64 and make them child of ProgramFiles64Folder and ProgramFilesFolder.

im not sure the ProgramFiles64Folder is default, but if not you can read it from env variables(less clean), like %ProgramFiles(x86)% and %ProgramFiles% or use hardcoded(least clean) paths you place in the PROPERTY table.

this is a technical possible solution, but i would consider it best practice to use 2 seperate MSIs.