Why can a USB Flash drive be formatted as NTFS or FAT32? Is the USB Flash Drive and Hard Drive just to be thought of as "an ocean of bytes"?

I get very used to hearing formatting a hard drive as FAT32 or NTFS, but we can also format a USB Flash drive as NTFS or FAT32?

Is it because a hard drive or Flash drive both can be thought of as "an ocean of bits" or "an ocean of bytes"? I remember RAM as: it takes 16 bit or 32 bit as an address signal (the 16 or 32 copper footing on the circuit board), and give out 8 bit of data (the other 8 copper footing on the circuit board). So can a hard drive be thought of as working that way too? So that's why a Flash drive can be the same too? Just an "ocean of bytes".

But is it true that hard drive's hardware make it an ocean of sector or something else, that is, the smaller unit of read / write is not byte but something else?

So with this "ocean of bytes", NTFS has the format that says, "if the first byte is __, then it means __ (it is a file or folder, and link to which sector, indicated by byte 2 and 3, etc, etc)"