EXT4 for very large (>1GB) files : increase block size, use block clusters, or both?

I'd like to format a 12 TB HDD (not SSD) **with EXT4**, in order to store large video files (each file being at least 1 GiB in size). I am working with an x86-64 (a.k.a. x64 or amd64) processor. There's of course the -T largefile4 option of mkfs.ext4, but are there other optimizations that can be done ? In particular, I wonder : - Should I increase block size to its max (64K, -b 65536) ? - OR should I use block clusters , and set cluster size to its max (256M, -C 268 435 456) - OR should I do both ? What would be the best parameters in terms of both disk space and performance optimization ?