Just got my Wing Sung 698 today. Since it is known to have a "soft" fine nib, here's how it compares to a Platinum 3776 14k Soft-Fine.
While neither of these nibs are true flex nibs, there is definitely some line variation to be had. Without pressure, both write very fine, the 3776 more so than the 698. To write with line variation, the 698 takes more pressure to flex than the 3776, but BOTH seem to produce practically the same AMOUNT of variation. Ie. the end result is the same, but how you get there is quite different.
Depending on your preference, the harder 698 steel nib may actually give you more control. As for the Platinum, the SF nib is indeed soft, taking very little pressure to flex. But the amount of travel the nib is able to safely flex is very short, resulting in line variation that doesn't come anywhere near a true flex nib.
The Wing Sung 698 is now my EDC alternative to the Platinum 3776.