Reformatting Ssds Mainly For Software For Backups

I am getting confused with some thing when it comes to reformatting drives.

I have 2 nvme drives and 2 Kingston SSDs. different sizes.

What i confused with is allocation unit sizes.

Performance Trade-offs:

Large Units (e.g., 64 KB, 128 KB, or larger): More efficient for handling large files (like videos or backups), leading to faster read and write speeds because the system makes fewer disk operations. However, they waste more space if many small files are stored.

Small Units (e.g., 4 KB, 512 bytes): Better for space efficiency when storing thousands of small files, reducing wasted "slack" space. However, they can be slower for large file transfers due to increased overhead.

For general use or mixed data, stick with the default size (typically 4 KB for NTFS or 128 KB for exFAT on large drives) to balance speed and space.

For dedicated large-file storage (e.g., video editing, backups), a larger unit size like 64 KB or 128 KB may offer better performance.

For small-file storage (e.g., code repositories, documents), a smaller unit size like 4 KB minimizes wasted space without significant speed penalties on modern drives.

When reformatting it will list sizes below
In MB
512
1024
2048
4096
8192


In KB
16k
32k
64k
128k
256k
512k


And there is these listed as well 1M and 2M which i don't know what they mean. I am not sure if they are Mb or not.They are listed under the KB.

I want one drive to have my games saved on the large NVME and and movies and music on the other with software.

Can anyone explain it better or am i missing some thing.