IIRC, we didn't have either of them when they came out. Expert was our highest stage back then. I doubt it'll be anything we can't handle. I honestly don't remember either of their mechanics. Nvm that, checked the old topic, Ultimate was introduced in Garuda, been too long.
If I remember correctly, Typhon recovers from debuffs at random, yea... at random. So Mordred is not recommended for her as she can clear all of them at once. Though her AI was terrible and would clear her debuffs when she isn't even debuffed, giving you extra turns. Think her overdrive gave her atk↑.
Garuda I think just hit hard but she was the first ultimate so no difficult mechanics I remember.
Ragnarok is what worries me since and the JP wiki is lacking information on both. There's some small details but certain information is left blank.