The hypothesis of physical laws being fundamental on a theoretical alternative universe is completely naive and meaningless from a philosophical perspective, because, while having similar objects (e.g. stars), it assumes that the the subject (the observer) is also similar.
Physical laws depend not only on the object, but also on the subject, which in this universe is invariably a human being with scientific knowledge.
In order to show you the fallacy, I assume that Immanuel Kant was correct, not only because his Critique of Pure Reason is one of the most representative definitions (if not the best) of the meaning of human knowledge, but also because my personal research in the systems theory conducted me to the same conclusions. Among them, that space and time are knowledge a priori of experience, and not absolute properties of the physical world. They would be absolute only if we consider that our rational understanding would be the universal absolute way of assessing nature by all entities that can not only get knowledge but interact with other systems (things) (including all the level 3 and 4 universes in the theory).
For example, thermodynamics is a beautiful theory, but it works only if we accept that objects (things) are fundamental physical natural manifestations. Put it simple, thermodynamics laws are correct only if we assume that our perception is absolutely equivalent to truth. We know that things are just an appearance, that the physical universe is not made of things. So, thermodynamics is an example of a set of physical laws that work perfectly... if we assume that the universe is made of the objects of our perception. More details on my answer here: https://philosophy.stackexchange.com/a/57718. Attention! This does not mean that science is wrong. Science is valid for the objects of our perception. [Personally, I think that quantum mechanics is perhaps the only science that faces such fallacy elegantly, although we're far from understanding the reasons that the subject defines the behavior of the object; QM assumes that our perception is not the truth].
This is a typical list of properties of fundamental physical laws, obtained from Wikipedia. Along with each property, a refutation of its meaning on a fundamental level.
[physical laws are...]
True, at least within their regime of validity. By definition, there have never been repeatable contradicting observations.
If we assume that perception is truth, ok. "Observations" require a human observer.
Another refutation to this concept of truth is given by Kant: there's no ultimate rule able to validate the rest of rules. "Within their regime of validity" implies "accepting that perception defines truth".
Universal. They appear to apply everywhere in the universe.
Absolutely naive and subjective. Universal does not mean only "everywhere" but also "everywhen". How would it be possible to be sure that physical laws worked near the big bang? By sending a scientist with a tester there and then? Again, this assumes we can extrapolate the laws that result from our perception to situations where perception is impossible.
Simple. They are typically expressed in terms of a single mathematical equation.
Obviously subjective. Ohm's law can be extremely complex for people with disabilities. Simple if the observer is a scientist with a degree. That would not be universal (or multiversal) at all. This implies that physical laws must be simple also for bidimensional neptunians.
Absolute. Nothing in the universe appears to affect them.
Obviously subjective. Depends on perception ("appears").
Stable. Unchanged since first discovered (although they may have been shown to be approximations of more accurate laws—see "Laws as approximations" below),
Physical laws would be stable within a subjectively assumed framework. Science is not the truth. But it becomes a truth sustained as a law since we perform subjective assumptions. Newton's laws can be true within some framework of assumptions (e.g. slow speeds), or can false in another (high speed). And if you think that Relativity is the ultimate law, be careful: there's some inconsistency between QM and gravity, which could lead relativity to be false within another set of assumptions.
Another refutation to this property would be this: how can a scientist can be sure that this is the same river than yesterday? How can he even be sure that the person he looks at on the mirror is the same person as yesterday?
Omnipotent. Everything in the universe apparently must comply with them (according to observations).
Works fine... if we accept that things are universal features.
Generally conservative of quantity.
Quantities depend on perception. This is a way of telling "hey, I see x things here and now". Ok, if dogs have 42 parts. Or if two persons can count the same amount of apples in a truck of apples in different states or maturation.
Often expressions of existing homogeneities (symmetries) of space and time.
Space and time would be "knowledge a priori of experience". Ok, if martians the size of a quark have the same knowledge.
Typically theoretically reversible in time (if non-quantum), although time itself is irreversible.
Time again, c.f. previous observation.
So, physical laws would be fundamental only if the subjects assessing such laws in others universes are also persons. With scientific knowledge. And with a similar set of assumptions (a priori knowledge). Can MW interpretation have universes with different laws? Yes, if persons can survive traveling to other universes, gathering observations performed using the scientific method, and bringing them back here. For a traditional scientist that assumes perception is the truth, this could have some meaning. But it does not from a philosophical perspective. Perception is not reality.