Flash makes it versatile against all sorts of stuff, including notorious card drawing permanents, planeswalkers, cascade, etc
its not possible to cast the copy as a permanent
We know they're underwater with a minimal amount of cues, which is both reinforced by the limited use of color and the lily pad vines we see
It is also awesome that CGC is willing to grade Gamma playtest cards (as for now just Gamma, as theres most information on them): 6 Likes zorloth January 13, 2021, 4:11pm 2 Super cool
Their +1 effect can be good as a game-ender, making a high-power creature unblockable attack for lethal damage so that the downside of the ability never even has a chance to resolve
All that alone would make Sephara at least a bit interesting for Commander, but the alternative casting cost really pushes it to another level