dectcarve:
Well, the first is a bit difficult, given that Myrcella is in Dorne and betrothed to Trystane Martell. The second is even more difficult, since Edric isn’t a legitimized bastard, only an acknowledged bastard. And legally, Stannis comes before either of them.
Why does Stannis come before Myrcella? Are we treating the incest as an acknowledged fact? Because in that case he came before Tommen too.
Legal precedent, following from Jaehaerys’ proclamation of 92 AC, the Great Council of 101 AC, and the decrees of King Aegon II, states that all male claimants, including collateral relations, come before a female. This was modified following the Blackfyre Rebellions to state that a female inherits before a legitimized male bastard, but after all legitimate male claimants.