Cloning microsd card to usb

I would like to clone the microsd card via dd so that I can make a backup microsd card. There is no room on the microsd card to clone itself (i.e. I m over 50% full - even with gzip compression).
So I put a large volume usb3.1 stick in one of the usb ports. Via parted, I see the disc. It is not mounted. It is in /dev/sda.
I want to do something like:
sudo dd if=/dev/microsd conv=sync,noerror bs=64K | gzip -c > /dev/sda/backup_image.img.gz

1- Since this is not NTFS, the largest file is 4gb and my clone will surly be larger. Should I format the disc to NTFS? Perhaps exFat is better?
2- In order to do the dd, the disc is supposed to be not mounted, correct?

If anyone can give direct comments on how I should do this (fat32 will not be good) I’d appreciate advice. Thanks.