So apparently most fantasy stories assume that -- outside of magic -- conservation of energy works, entropy happens as expected, spacetime is mostly just plain spacetime and there are apparently plants and metabolisms and so on. The whole point about magic -- what makes it magic and not physics -- is that it violates basic physics, but not (generally) most of basic causality.
A lot of what we "know" about the laws of physics is what we think we know: we do not know things 100% of the time in 100% of situations. The physics and math that was used to build the pyramids thousands of years ago was "correct," but it didn't take into account things like relativity or quantum mechanics. But just because the Mayans and Egyptians didn't know about quarks or radioactive decay doesn't mean that the science/math they knew was wrong: it was as much as they needed to do what they had to in their situation. When electrical engineers first started creating semiconductor circuits, they weren't thinking about quantum mechanics, but now they do since we've made circuits that small.
So a wizard making a fireball doesn't need to worry about the laws of entropy the same way you don't think about it when you light the burners of your stove. The universe's rules run in the background, regardless if you know how they work or not.
Of course you could propose magic that doesn't need any energy and/or doesn't displace anything or interact with anything in a destructive way BUT wouldn't that magic be completely unconstrained? On the other hand, if magic can potentially interact destructively with the "real" (physical world of basic physics) and its power has some impact on whatever sustains the natural world, then potentially the magic could run away and destroy the universe. Given that we are talking of a limit to magical potential -- in such a case magic would need to face some magical mechanism to constrain it at least in universes that are not destroyed by run-away magic.
You can make the same argument about atomic energy. People believed that the universe might implode when we turned on the Large Hadron Collider. Who knows what the "laws" of physics even looked like when the universe first came into being?
Full disclosure: I do believe in the metaphysical aspects of my religion, which you cannot
prove objectively 100%. But you also can't disprove it.
Hawking's final paper discussed the possibility of multiverses existing, but we can't prove or disprove it, but if it does exist, it will exist regardless of what we think we know. There could easily be a big flaw in our understanding in any of the laws of physics because of assumptions: how could ancient mathematicians know that
g would be different by a black hole or on a different planet? But what they knew worked for their applications and situations. What we currently know about how the universe works is based on our current measurements, senses, and abilities; it can and will change as we make more discoveries, but it doesn't mean that those rules don't exist/apply until then.
Anyways, back to magic. The "scientific definition" that I have for it in [birds] is "the application of one's will/intent on energy in a manner that causes it to deviate from its natural processes." (With enough time/patience/bananas) you could train a monkey to strike flint and steel and make fire, as the "rules" of the universe are running in the background to cause the physical/chemical changes/reactions to start a fire. An object will not spontaneously ignite without something entering/changing its system. But if you psychically/telepathically create fire with magic, you are doing
something with the rules of the universe, but you probably don't know what, you just know that if you think [x] then you get [y]. To the monkey, the flint and steel are magic, too, because it doesn't understand what's going on. It's introducing something into the natural system that isn't normally there.
Zero Escape discusses a lot of metaphysical concepts that I think are relevant to your questions. If you gave a caveman a wireless computer display, if they open it and start to cut wires, they would think "ah, these cause this device to work. Something about these connections cause this device to think." But we know that's not true, the display is just showing information that is being calculated/rendered at a computer somewhere else, which is being transmitted wirelessly to the display. The caveman only destroyed its ability to receive/display those signals; the main computer remains unchanged. What's to say that our consciousness/souls don't exist somewhere else and our brains are just the receiver/renderer of the signals? The energy of the signal can be in an energy or form we cannot see our measure, just like how a caveman cannot see/measure Wi-Fi. But It Just Works.
Why doesn't magic tear the universe apart? Who knows? Does it matter? Unless the character is a theoretical physicist and they're trying to answer these questions, it doesn't matter. A universe that "evolved" (and/or was designed, depending on the cosmology) with magic/energies/laws that don't exist within our own has checks and balances, just as ours do. Magic in fiction is magic to us because we aren't familiar with it. People used to think the wireless communicators on Star Trek were "magic" sci-fi tech, like how we think of teleportation today, but we all own multiple wireless communicators that fit in our pockets. Atomic energy was "magic" for quite awhile, and still is in some cases (looking at you, super hero origin stories).