I used a USB key for the 1st option (recovery) and tried both USB key and USB hard disk with the same result for the 2nd option (drivers).
I've also tried 1st option with an old SATA disk and plugged it as usb using a sata-to-usb dock. It worked fine too.
If I have time to spend, I have try to remove the SSD and reinstall the original HD before retrying the 2nd option to see if it's really buggy.
The driver disk is less important because we can download the last version of drivers on the asus website, and they'll be newer as the original ones.
If I have a lot of time to spend, I will change the SSD by a newer and bigger one and try to use the recovery usb key to reinstall. I'll have to reinstall all my applications after that). And because I use my laptop daily at work, I have to wait for holidays...