So Herrcher of the Void form will have different profile or.............., beside i think using 2d artwork(like the art you use for White Comet) for profile better than in-game 3d art
About speed, i think Kiana or someone on par with her is Supersonic+ to Hypersonic. slow Valkyrie like Bronya is Supersonic to Supersonic+, fastest Valkyrie like Mei or Sakura i think is solid Hypersonic. the only one i'm confuse is Fuhua, she have a panel where is launch Knight Moonbeam Kiana to the sky in a short time, which the distance is unknown, and we don't know it is her casual speed or short-burst full speed
More info, Sirin when 2nd Impact summon a meteorite which is City level+, but that was when Sirin was a full Herrcher, Knight Moonbeam is not her full power and Voidrifter is Kiana using some of Sirin power, they below Herrcher Sirin, so i think Low 7-C to 7-C is more reasonable, even the series admit that and S-ranker have a low chance survive an encounter with a Full Herrcher, even Kiana's Mother Cecilia using God Key never fight Sirin, the only one who fight Sirin to a stalemate is Siegfried using full power Judgment of Shamash turn him into a MANTIS, S-rank Valk still don't have feats they on par with a Full Herrcher, so i don't think 7-B is reasonable with S-rank Valk, unless Full Herrcher is stronger than 7-B
Edit: Well i think just keep speed range from Supersonic to Supersonic+ for most character, need more evident for Hypersonic though