I recently ran into a situation where my SD card for my DSLR is full. I had already taken a backup of my photos inside the card and from what I have learned after reading some of the guides online that first formatting will erase the files permanently. And secondly, format types are kind of different in a Mac, than on a Windows machine.
Why not save all the confusion and just format it in the camera?
Both Mac and Windows can read, write and format exFAT, but you need to make sure you are using MBR rather than GUID and the correct sector size that the camera prefers.
Rather than have to work all this out, especially if you're not even sure what they mean… just let the camera do it instead. The camera will also by default add some special folders it needs (DCIM and additional folders inside that) that neither Mac nor Windows will know to create.
If you format in the camera itself, neither Mac nor Windows will have any trouble with the card, and the camera will be very happy too.
I can only strongly recommend not to format the SD card for use in the camera on a Mac or PC. A lot of write failures that I hear from in the Fuji and Sony context (including freezing of the camera itself) have been traced back to SD cards that were not formatted in camera.
Telling us, that you ran into a full SD card and are only now creating a backup of it, shows me that you use the card to actually keep the photos permanently on the card.
I can only plead you not to do that. SD card failures are quite common. Almost every photographer that I know, had a failure eventually. There is a reason after all, that especially wedding photographers always demand 2 card slots in their cameras, just to have a backup if the main card dies during a session.
See this research of SD cards failing by Tony Northrup: https://www.youtube.com/watch?v=qqo-MtNy2Ps
Best practice is to copy all files from the card to you hard-drive as soon as possible and then reformat in camera, making sure the card is good to go and in the exact format that your camera likes.
SD cards are cheap, but photos and the connected memories are precious.
As noted in another answer, all major operating systems (Mac, Windows, and all Linux distributtions) can read, write, and format XFAT -- but it's probably better if you don't format your old cards, whether from computer or in camera. Keep them instead, and buy a new one.
Your 64GB SD card will probably cost less than $20 if you don't get it from a camera store (if you do, it might be five times that figure). For that price, I'd consider it worthwhile to keep the original card, like keeping negatives in file pages in a cabinet. Sure, this gives up the "bad frames are free" paradigm of digital, but it means you can go back and look at what you didn't like on the frames you didn't originally decide to keep, and learn from your mistakes.