It’s interesting to compare vintage flex nibs to modern flex nibs. My preferred, unmodified modern flexible nib is the OMAS extra flessible nib (in this case, an extra-fine). The OMAS nib is a 14KT gold nib, just like the nib on the Waterman 94 I compared it with in the writing sample below. The vintage nib felt softer, bounced back faster, had better feedback (i.e., it let me know when I was pushing it far enough), and the ink flow kept up well. Flexibility will vary, but you can certainly find a nice, soft, flexible nib if you want one. The modern nib was quite decent, but if you want a truly flexible nib, I’d say go vintage.