I never went very far into SimEarth (I remember getting a bunch of maxis’s simstuff in the 90s, and not having the patience to really get into some of them back then).
However, I did play Spore during its prime. It’s very shallow, on all levels. Don’t expect any kind of simulation in there, especially not physics or even basic biology and evolution really.
Its whole gameplay loop : design a beast, eat or make friends, be a tribe, fight or make friends, design a town and vehicles, fight or make friends, design a spaceship, fight or make friends and try to reach the center of the galaxy because I don’t know.
You can manipulate planet atmospheres in the space phase, but there are no variations : you can basically make planets “suitable” for life, and all life in the game needs the exact same parameters. There is zero room for experimentation and everything is basically just as efficient as everything else.