In regards to the power of the ringworld start. One of the things that has always bugged me in regards to ringworlds in general, is that one doesn't need the galactic wonders perk to fully benefit from the perk. This is also a issue with other perks. Some that come to mind are world shaper, mastery of nature and project arcology. Anyone without the perks can get the full benefit of things that those perks provide access. Project arcology's only real advantage is that you get to decide what gets turned into an ecumenopolis. Mastery of Nature and World Shaper are slightly better, since some of the perk is exclusive, but the most powerful parts are still free for plunder.
Anyways, what if the 10% production bonus for Gaia worlds was only given to those that had picked world shaped? Granted, life seeded origin would definitely need to be buffed, it would help make the perk more valuable. Ringworlds provided less resources for those that don't have the galactic wonders perk? This would reduce the power of the shattered ringworld origin. Could even do something like have it be a 10% malus without the perk, but have it so that if you restore a ring, you get the empire modifier ringworld restorer, which reduces the malus to 5%. Not sure how you'd go about tweaking Mastery of Nature. Maybe getting the perk gives the Mastery of Nature empire modifier which reduces all malus costs that the Mastery of Nature planet modifier incurs. Then maybe remove the influence cost, reduce it or have it cost something else and give empires the option to remove the modifier, but actually have that cost influence. The malus could increase the upkeep cost of all districts and double their sprawl value. Just spit balling ideas here, but Voidborne was a fantastic change, in part because it remove the nonsense where an invasive empire could get the best benefit of the perk, provided they waited for a target to take the perk and build habitats. Once the chance went into effect, they could no longer get the best feature of the perk and in fact, that created a scenario where they'd run into issues because not only would those two building slots go puff, but it could even throw them into a scenario where once those go puff upon successful invasion, they get saddled with other issues because of what building got nuked.