FAT32 can be applied at will to any NTFS or HFS WD disk drive. There are no limitations related to how many times you can change the file system back and forth between NTFS, FAT32 and HFS beyond considering the disk drive will be completely erased every time you change the File System by means of re-formatting the disk drive.
FAT32 will not allow you to copy individual files larger then 4GB. It will accept folders with total size beyond 4GB as long as an individual file within said folder does not exceed 4GB.
For additional limitations related to FAT32, please visit the following link:
In order to format/partition a WD disk drive into FAT32, please visit the following link: