the "Object Mesh Data" Node has a hidden input called "Vertex Normals". Press n to open the properties panel in the node editor and activate the output by clicking on the little eye icon.
you can then use a vector math node to scale the vertices along their normals. shuffle the vertex list and remove all but the first vertices.
Parameters to control the output:
- Scaling factor of the first vector math node: there you can control how far away each point is from the base mesh
- Node Seed of the shuffle list node: shuffles the list in another order, other vertices get deleted from the end of the vertex list
- end of the slice list node: controls the amount of vertices that don't get deleted
node setup with splines (like in your reference image):
Let me know if you need anything else or a deeper explanation