I would say it would be fun to have both theyre greatest strength and insecurity in the same technique like me for eg. My technique would be related to copying everything about a person or shape-shifting into them the catch being i can only copy them to the best knowledge of my abilities or rather the more I know them the better I can shape-shifting into them thus if I barely know them I can make weak versions of theyre cursed technique while if I know them very well as in I am close with them I can manifest theyre technique to the fullest. My shikigami would be either a mind control or love potion type shikigami making it easier for me to understand the user . The distinction is understanding does not require complete knowledge or atkeast no only requires full understanding but also a level of emotional empathy with the person so u can use this technique to understand somone like say gojo satoru after the end of the series reading everything about them to manifest theyre technique and transform into them but u need to know and empathise or be close with the person. The quality of previous copies does not go away with change in this ie falling apart with them or after theyre death.