With a little thought, it is easy to figure out WHY Ryu and party would reject Myria's offer. Teepo and her believe that the Brood's power could only be used for evil. However, Ryu is never shown to commit any sort of evil. Think about it. There were a dozen instances where he could easily have become a conqueror. He killed Balio and Sunder, he is capable of intimidating anyone who comes near him by going into dragon form, Rei could easily have killed Mikba and taken over his criminal empire, Rei could easily have murdered or enslaved the McNeil residents, the party could easily have killed or imprisoned the king and queen of Wyndia and taken over the kingdom, the party could easily have ruined Rapala's economy by seizing control of the lighthouse, Momo could easily have taken control of the Middle Seas with the Black Ship effectively controlling half the continents economies, Momo could easily have taken the robot army under her control from the towns across the sea, the teleporters would make many areas opened up to sudden hit and run raids, Ryu's power could destroy any army, the entire party is able to kill Myria, a practical god, and the Brood could have easily taken over the world if they had been so inclined. Let's face it, within a decade, Ryu could have been the emperor of the entire world with little difficulty and could convert many people to his side with fear tactics. He logically KNOWS he could have done this at any time and yet, time and time again, he's used his power to try to help people and protect his friends. Myria's whole argument that Ryu's could ONLY be used for evil completely fell apart, debatably, after the events of the entire second half of the game. The fact that Ryu exists and is a good guy is proof enough that Myria is wrong.
While it's a standard game mechanic for the hero to fish in Breath of Fire, where does this Ryu learn how? Simple: There is a year-long timeskip, and he knows Bunyan, who wants Rei and company to earn their way rather than rob people. It's not a stretch to assume that a hermit like him would know how to fish, so he could reasonably be expected to be capable of teaching other people how to do it too, and the timeskip would give him enough time to do so with Ryu. As to why Ryu asked him to teach him... well, even Bunyan can't complain about you eating food you gathered yourself, right?
Why is Rei willing to use the Weretiger form later in the game when he refuses to do so in the beginning? Because you fight him as a boss shortly before he rejoins, and have thus proven that you can take it.
When Garr talks to the Patriarch of Urkan Tapa, he's asked if he's going to enter his long sleep. When he replies positively (though he doesn't mean it), the Patriarch explicitly states that evil must therefore be gone from the world, which Garr doesn't argue. Except Garr knows that that statement is false, since he saw the evil of Balio and Sunder up close. Garr is already doubting his faith, and plans to bring Ryu to Angel Tower to find the answer to his faith: he knows that Ryu can effortlessly kick his ass, and hopes that Ryu will, to find the answer to his Driving Question.
The fact that Jono prefers Nina to Momo could suggest that the attraction between the Dragon and Wing clans might not be limited to the various Ryus.
Why is Myria more humanized here than in the first game? Because she had a son in the second game, in whom she poured all her hatred and evil into — and your ancestor already defeated him.
Fridge Horror
Bunyan wasn’t necessarily aware of Rei’s powers, and he made no effort to stop Teepo and Ryu from following him to Mt. Glaus, so it’s possible that he sent them after the Nue with the expectation that they wouldn’t make it back.
