How to format multiple exFAT partitions on USB drive?
To format an ExFAT partition, unmount the partition and use (sudo) newfs_exfat [options] /dev/disk*s*. Check man newfs_exfat for the options.

The default FAT-size is 32bit, so you don't have to (or more precisely: you can't easily) specify the -F option.

Typically the Terminal commands should look like this:

diskutil list #to get the disk identifier of the exFAT partition
diskutil unmount /dev/diskxsy
sudo newfs_exfat -v Name /dev/diskxsy