I advice you to just use /etc/fstab to mount the drive. Here is how I mount my usb drive in fstab:
UUID=c3d75b82-765d-4924-accc-d23cd3c938ef /mnt/ToshibaHD ext4 nofail,x-systemd.device-timeout=1ms,defaults,noatime 0 0
Use the UUID for your drive, you can find it withe this command: sudo blkid
Make a folder somewhere in your home directory to mount the drive or in /mnt but if you do in /mnt change the ownership to your username. If the drive is not formatted with ext4 then that option should also be different.
The nofail option is to make sure that even if the drive is not connected there wont be an error. So unmount the usb drive and modify your fstab and before you reboot check if everything is ok with sudo mount -a
Your drive should now mount at the given mountpoint.
I chose a quicker, dirtier route. I reformatted the empty drive with everyone as an option and bypassed the root only access. But I learned a lot.
As to your question, I wasn’t sure which extension to use, BRTFS, EXT4, etc. I chose the later. I don’t care about exporting it, although as I say this, it’s big enough to have a Vorta backup and a manual uncompressed one.