>in (1)..., the observer is just other particles.

It has been proven that non-concious observers can trigger a wavefunction collapse through variations of the dual slit experiment. What we don't necessarily know is exactly how the chain of wavefunction collapse occurs from e.g. the "opening of the box" to e.g. the human eye. This is known as "the measurement problem".

Also, fwiw, in both the Copenhagen interpretation (1) and the Many Worlds Interpretation (2), the observer is simply any particle which measures the event. It may be more intuitive to say that as soon as particle/s depend on knowing the answer to the wavefunction collapse, it will collapse.

This may be "fuzzy" as well meaning that if the particles don't need a precise answer only the amount of wavefunction collapse needed to give that level of precision will occur.

>Now in (2) isn't this the same as the problem with (1)? the collapse happens near instantaneously and so these other worlds are fleeting possibilities that never really existed, its the same fallacy as the cat in the box never really being dead

Many Worlds Interpretation posits that the _all_ other worlds absolutely exist before and after the collapse. After wavefunction collapse, each possible outcome occurs in a separate world. The one that "we see" is merely one outcome being experienced. Indeed, the reason this may be confusing is that you have to realize that other versions of yourself will see the different outcomes, each one convinced that they're the only version.

It can sound kind of crazy and we have no way of proving the existence of these other worlds but the interpretation is still taken seriously by many in part due to it being the most literal interpretation of the Schrodinger Equations.

>the wave form collapses in a small delta of time, and provides the continuity we see in the macroscopic world

You refer to this as a "problem" i.e. that these collapses are vanishingly small and so we never encounter them. But we can in fact encounter them!

Imagine shooting thousands of bullets through two slits with some degree of known error in aiming. The wall on the other side of the two slits will likely have holes in two vertical lines.

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This is also what happens when we measure a photon before it enters the slits. It behaves as a particle would.

Now imagine you push liquid water through the slits instead. The water forms waves as it passes through the slits. The peaks of the waves when they hit the wall on the other side form something different that looks like this instead.

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This is what happens (after shooting multiple photons) when we make no such measurement of the photons.

Now, to us, each photon comes out in different spots instead of all at once like with the wave. The first might be

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And then

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But sure enough, with enough photons it will eventually appear as

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This means that either:

Copenhagen:

A pretty literal wave of possibilities travels through the slits. When it hits the wall, this so-called wavefunction collapses into a single point. That point will be statistically likely to land somewhere on the many-lined diffraction pattern.

Many Worlds:

Multiple worlds exist in which each of the single points follow the different trajectories we see. They still form a diffraction pattern because these worlds are defined by the same Schrodinger Equations that may also define the wavefunction collapse.

There's a lot more that I'm skipping over such as Pilot Wave Theory which posits that each particle was in fact always a particle that instead is guided by a "pilot wave" that can sort of see the future, or travel faster than light in order to determine where it should land. Ultimately what I'm trying to say though is that there is no way around quantum mechanics. Yes, the timeframes are tiny and the cat probably isn't alive and dead at the same time due to decoherence occuring well before you open the box; but reality is still very much quantum and there are ways to observe that.

It's weird af, but it's absolutely happening.