Is there any state where someone doing this would potentially face
manslaughter or murder charges, due to some variant of a 'life starts
at conception' anti abortion law?
Not really. Those laws are currently unconstitutional. A state could certainly prescribe some criminal punishment in a case like this one, but punishing under existing manslaughter or murder laws would almost surely not be upheld under existing law (subject to change without advanced notice by the U.S. Supreme Court).
If someone knowingly and intentionally destroyed an embryo conceived
via IVF but not implanted yet what kind of consequences do they face?
Is the potential life treated differently or is this just destruction
of property?
This is a tough question that probably doesn't have a uniform answer under the law of all U.S. states.
For one thing, it isn't clear who, if anyone, has property rights in the embryo. It is certainly conceivable that a state might instead conclude that the donor receiving the IVF treatment has only contract rights in it (and breach of a contract is not a crime).
It might be viewed as a property destruction case. There might be a specific statute on point. There might be a civil lawsuit remedy. In most states, this would be an issue of first impression and a court would look a competing ways that cases had been handled in other jurisdictions to decide what to do in its case.