a full cap would require shaving.
yes, you can use small clips to attach a topper piece....but you should know that they can cause traction alopecia in some people, meaning that the clips could damage the hair further in those areas where they attach. it is recommended that you move them around every month or so , so they are not always effecting the same strands of hair.
I would recommend an all french lace piece and sewing the smallest clips onto the base.
you would not want to sleep in the clips so you would lose that option .....but its definitely do-able as long as you know the ups and downs of it.
DebbieS.