Try 0.1.

If he used the small card for display only and the bigger card for rendering, would that allow the full use of his 12GB?

C4D is well known for slow View response (I know Maya is faster). I use the LV to see changes when the scene viewer is reverting to boxes.

What is the difference between "proxies " and render instances?

It would seem that crippling the use for commercial purposes would relegate the Forester utility to amateurs. They would need to warn you upfront.

It would need someone very knowledgeable about the software. Maybe not too thick on the ground.

A cursory glance at Help left me feeling your complaints are excessive.

You may find that displacement only works with height maps.

Perhaps a change in light direction could help.

Sounds like you may have found the problem.