Most of the ones out there are at least F-3 to F-10. Thats why there are all those great colors.
The last time I bred a pure flavi to a pure argus was about 10 years ago. All of ours are indeed products of multi generations, so yes, they are indeed fertile.
On a side note, one of our original female Argus/sand crosses is now gravid with her 52nd clutch, man that is kickin it. The Male is the product of one of her offspring, bred to a goulds(=threeway), then bred back to a Argus/flavi(twoway). So their babies will be 5ways(addition) or 6ways(multiply), ok, they will still be three ways, argus/flavi/gouldi. Thanks FR