Q: 

Are all QFN64 EFM32 parts pin compatible?

A:

All EFM32 devices with the same series number (840 is the series number of the EFM32TG840F32 for instance) are pin compatible. So a EFM32TG840F32 will be pin compatible with an EFM32GG840F1024, but not with an EFM32TG230F32, even though both are QFN64s.