Ignore Quad Density/QD floppys. If you must have 720KB on a 5.25" floppy, use a High Density disk.

Here are the basic rules of DD disks in HD drives :

You can read a DD 360KB disk in an HD drive, assuming the disk is not copy protected. You can write to new and unformatted or degaussed DD disks, but don't expect reliable reads or writes in a DD drive. You should never write to disks with data on them or which have been previously formatted in a DD drive.

The drive does not detect automatically if you put a DD or HD in.
DOS format.exe tries by default HD on a HD drive, so 1.2 MB as set in BIOS. Applied to DD disks this gives you a varying lower capacity and can be considered unreliable and not useful.
You have to tell format.exe to target a DD disk by setting switch /f:360.

One more detail is there: HD drives use higher magnetic fields for writing since HD disks usually are hard-sectored. DD disks instead are usually soft-sectored and real DD drives use a lower current thus a lower magnetic field. Using a HD drive for writes on a DD disk works, but trying to write on the same disk later with a DD drive may fail.

So its not recommend to use DD disk?
The only i want to use DD 360KB is for simple cga / ega dos games that are about 200kb or something like that.
I think its not usefull to use 1.2MB disks, then i could better using 3.5 inch disks...