What is the Max number of Nodes a scene/level should have according to P3D’s standards?
As far as nodes go, I don’t really think a high (even greater than, say, 10,000) node count will hurt your game’s performance. What will hurt performance is a high geom count, but that’s usually easily resolved with flattenStrong().
Nodes don’t directly cause performance issues, it’s the number of geoms that are (partly) in view at any given time. This shouldn’t be more than a few hundred. You can use PStats to monitor these things.
Keep in mind that flattenStrong can cause performance drops when not used correctly, because culling can no longer be performed on flattened nodes.