VIs stack with other VIs as well.
If you felt like it, you could fill up a huge planet with VI3's and get 75% more resources (almost double!) your resource value every ten turns.
At one point, solar generators were depleting the planet's resources, but it was fixed in v1.59
Finite resources on PBW can be pretty interesting. There are meaningful trade-offs between the time and investment needed to get sustainable production, and just draining a planet dry. Trade income and storage become more important. I would say that Religious should probably cost a little more in a finite resources game, and would tend to recommend High or at least Medium research costs. Maintenance reduction ability is also massively important.