I found that placing two flux points next to each other caused my FPS to drop from about 120 to 20, any more plugs next to each other would cause the game to be near unplayable. I think a large number of flux points may also cause fps issues even when not placed next to each other. I was using Rivens algorithm and also tried rivens half and full but the issue persisted.

You must have been using an outdated version, pre 1.12.2, issue should no longer be an issue due to plugs using minecraft's default block renderer