Ideal bytes-per-inode ratio for a large ext4 partition

I'm willing to create a 8 TB ext4 partition for storage. I've created it without su reserved blocks

# mkfs.ext4 -m 0 /dev/sdX1

but still, 58.89 GiB were occupied with nothing written in the drive.

I understood from this post in the Arch Linux forums it was because of a low bytes-per-inode ratio, but the wiki page didn't clarify all my doubts.

1. Is the only downside of a high inode-per-bytes ratio the risk of ruing out of inodes if many small files are written, thus being unable to write any more files?

2. Or, if I create a filesystem with a 6 MiB ratio every file below 6 MiB will occupy 1 inode and therefore 6 MiB in my partition?

3. How to tell which must be the mean file size to avoid ruing out of inodes?

I know I'm making an awful confusion between inodes and sectors/blocks, but reading what an inode is really didn't clarify my practical doubts.

Here is the output of fdisk on my drive

# fdisk -l /dev/sdc

Disk /dev/sdc: 7.3 TiB, 8001563222016 bytes, 15628053168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

For the record, creating my partition with a 6 MiB ratio resulted in just 1.12 GiB being unusable.