Only certain parameters of instances can be modified. For some reason, you can’t move or resize layers within an instance. There are some workarounds (i.e. using auto layout within a component to move the X,Y position of layers, or duplicating the layer resizing it, and using visibility to turn it on or off), but these workarounds require a lot of extra steps. This is a basic feature in other programs (i.e. Adobe XD). I’m confused why this isn’t an option in Figma.
*No pic included because I think this is self explanatory. Let me know if it isn’t.