Currently the horde movement speed seems to be hard fixed, if possible I would like to have a config to set their speed, or maybe in the datapack each of the monster type can have different movement speed eg
{ "entity": "minecraft:zombie", "weight": 10, "first_day": 0, "last_day": 0, "speed": 1.5 }

You can already do this with nbt https://minecraft.fandom.com/wiki/Attribute.