To change the movement speed settings in SGKv1 go to the BP_PlayerInventoryComponent, then go to the Class Default and search for Movement and you should find the settings shown in the image below, here you can set the movement speeds for each player state.

When using a holdable the characters movement speeds are controlled by the weapons blueprint to change those settings go to the weapons holdable blueprint, like for example the BP_M4A4 and in the Class Defaults search for Movement to find the same settings there.