Try exFat on a card (which is used in Linux) and you will ruin the card!
Buy a larger capacity micro-SD card and insert it into the card reader and see what you get. You are going by the maker of the card itself and not the reader that reads the cards.
I trust the card maker not the Internet. Do as you want just give accurate info please.
There are two different discussions going on here: the maximum capacity supported and the formatting of the card.
Regarding the formatting, Here is how it works:
For 32 GB cards or less any format is valid
For a 64 GB and greater only exFAT and NTFS is possible. If you do some research in the Web you can find tools that allows you to format the 64 GB card as FAT32, I have used them with good results.
I personally prefer NTFS because it's a more robust format but then you may run in incompatibilities if you try to use the card in a phone or camera.
Most 64 GB cards come formatted as exFAT which also have some compatibilities issues with cameras and other devices. An example, Toyota cars do not recognize this format in USB sticks, only FAT32 or FAT16. But in the case of Windows RT, all these formats
are fully supported.