Randomising input of geometry node, instantiated via "Instance on points"

Question

I have a geometry nodes setup to procedurally generate a tree. The nodes take a series of values for group input to modify how the tree is rendered; some of these are fields, some are simple values.

In a separate geometry nodes, I want to instantiate all these to a grid, or something else that has points. I don't want to manually create a collection, make a load of variations, and then load the objects in from said collection - I'd rather do it all purely through GNs.

The issue I'm having is that the values I put into the node of nodes is the same for every instance:

If I try to randomise a value, it either gives the dreaded red noodle (tree height) or just applies exactly the same for all (bumpiness, bend, seed, etc)

I can randomise all these values perfectly fine if I import the blend file in bpy and modify the values in python, but I want to be able to understand how to do it this way.

Even if it were possible to shift+d a few "geometry nodes" nodes and group them all together with a "make collection" (doesn't exist) type node, that would fulfil the same thing as doing it using actual objects in an actual collection inside the main blender tree.

Any thoughts or help would be much appreciated.