So the way I see it is
-If you are summoning something you create, there is not much energy left for you to do big spells
-Summoning is the main ability of shadow witches
-Common spells include: Minor cleaning and basic stuff similar to it, very weak telekinetic powers and energy balls.
-Shadow witches specificly have: Shadow balls, minor invisibility, summoning, conjuring (summon: already exists/ Conjuring: Make your own) and preventing light in a room (make a room dark, won't work outside, the sun is too strong and so is the moon)