You should not have to add a component of a parent class to the children to be able to modify it. All of the components and variables of the parent class should be exposed.
With regard to sprite components, I am not sure. To be honest, I don’t use any kind of sprite component when I do sprite stuff. I tend to make a unit square mesh (0-1) with 0-1 UVs and then manually set up all the camera facing behavior in the material which gives me better control. You can use camera left vector (1,0,0 transformed from view to worldspace) to get the X facing component and camera up vector (0,1,0 transformed from view to worldspace) for the Z facing component. Then constantbiasscale the UVs from 0-1 to -1 to 1 and use the X and Y component of the UV’s to multiply the camera facing amount.
Then you make a scalar for width and multiply it by the X component, and scalar for height multiplied by the Z component and add the results. Then subtract worldposition and add actorposition and plug it into the WorldPositionOffset input. The reason I do this is for control. You can make 1 mesh that has 50 sprites built in that all move randomly within a defined bounds and then all conform to the shape of the underlying terrain using traces and splines… just one example I did recently.
I just did a super quick test using the Billboard components and I was able to adjust them via variable. I changed the texture using construction script and it worked. I created a child BP and saw the billboard component to edit. I tried to change the sprite UV’s and that did not work, however. What exactly did you try to change that didn’t work? Maybe a bug…
Maybe you had the billboard as the Root of the parent? Try making the root a blank staticmesh and the billboard component the 1st thing under that if so.