You need to keep in mind that with either the bad flash recovery method, or the soldering method, that you are able to dump your drives original MS28 firmware and therefore get your drive key, which can use to add to a hacked firmware. You still need to edit one of these hacked firmwares with your drive key, so that it will allow you to play your backups.
You can play your existing backups, and new backups, as long as the firmware that you flash your drive with, has your drive key at the right location, and it has been edited or hacked to read the security sector of the game that you want to play from the right location, (which is at a different location to the original).
The existing hacked Samsung firmwares have had this done, and if you use one of these to flash your drive then your backups will play as long as you've put the security sector in the right location on the disc that contains the backup.
If you don't want to have to reflash your drive with either, the bad flash recovery method, or with the soldering method, each time you want to get your drive detected, in Windows with xtreme0800.bin. Or when you want to change your drive back to read backups with xtreme.bin or xtreme_proper.bin. Then you should flash your drive with the xtreme20.bin.
You will need to manually hex edit xtreme20.bin (and xtreme.bin for that matter, if you want to use it), if you want to flash your drive with either of them. xtreme.bin and xtreme20.bin have not been patched to work with KDX 1.5. Only extreme_proper.bin has been patched to work with KDX 1.5.
I would recommend flashing your drive with xtreme20.bin, because you will only have to flash your drive with it once. You can then use the enable0800 disc to get your drive detected in Windows each time you want your drive detected in Windows.
If you use xtreme20.bin then you wont have to flash your drive again and therefore will only have to do the soldering method or the bad flash recovery method once.
If you use xtreme.bin or xtreme_proper.bin you will have to reflash your drive everytime you want to change modes of the drive, which will mean that you'll have to use either the bad flash recovery method or the soldering method every time you have to reflash your drive.