There are more than 4400 systems, it would take you several centuries in game time to survey them all. Even if you did it would be possible to change to using random stars and crank up the max number of systems, however I think by this point the game would have set your computer on fire so this is mostly an academic question...
If you are worried however you can turn up the ruins generation chance, as dormant constructs will generate randomly with ruins. As a bonus this means more Precursors to slaughter and loot.
The 30% NPR generation chance is normal, but it does not mean 30% chance per system, rather any suitable planet (one which is close to zero CC) has a 30% chance to generate with a NPR. As these kinds of planets are quite rare, especially in known stars games, you will generate such NPRs rather infrequently.