Hi Krishnan,
I always keep my installer as 32bit (ie compiled as x86 platform). I use a customised version of one of the B1DE installers, It will work perfectly well installing either a 32bit or 64bit addon. If you do want to create a 64bit installer then you need to make sure that the installer calls AddOnInstallAPI_x64.dll at the end of the installation, rather than AddOnInstallAPI.dll.
When generating the ard file for the installer, there is a new property that defines whether the addon is a 64bit addon. This is included in the new version of the AddOnRegDataGen application.
For the addon itself, I compile for the x86 and x64 platforms (Any CPU would also work fine for 64bit).
Kind Regards,
Owen