JBW: "The 'measurement' of a property does not 'exist' until a physical setup is arranged.... This makes way more sense than the subjective belief that a particle's property doesn't exist until it is observed, which is about as unscientific and laughable a statement as I can imagine."
Strictly empirically speaking these statements are more or less equivalent, depending I guess on how you might choose to interpret the term 'to exist'.
It is correct that measurements of particle properties are only potential measurements until the physical setup is ready and the actual observational event takes place. The difference here is between potential and actual measurements, where the former can still be said to 'exist' in the potential sense. Potential events still need an actual physical setup, a world or an environment, in order to be a potential event. That is to say, their potentiality is derived from the actual observer's world they might take place in.
But likewise for the "assertion that particle 'properties' do not 'exist' until measured." A particle's properties are only potential properties until they are actually measured and become the actual observed properties. This is simply an empirical fact of the matter.
In both cases the 'existence' is potential until it is actualized. And this is true whether or not we're talking about classical particles with discrete properties or a superposition of non-commuting properties. The actual event of any potential observation / measurement is what makes any potentially measurable properties ... actual.
But it seems to me that you want to assert something more about that potential existence--that while potential events don't really exist until they happen, a particle's potential properties do really exist independently of whether they are observed or not. Would that be correct?
If so then this is a much stronger metaphysical claim concerning the 'real existence' of an unobserved particle and its properties, and I take it you lean more towards the realist side of Einstein's position as opposed to 'laughably unscientific' notions concerning what can or cannot be said about the non-classical reality of quantum properties? You would include for example a Many Worlds interpretation in your 'laughable quantum mysticism' category?
As a radical empiricist, all I can say is that a particle's classical or non-classical properties exist only in the potential sense until an actual observation is made, and that that potentiality is what is 'real' most especially where a quantum superposition is concerned. Which I take it is where we might diverge, as from this perspective no actual properties can exist independent of our potential empirical observations. Simply put, there can be no empirical evidence for the reality or otherwise of an unobserved particle's properties, and observation is the key to this historical conundrum!
JBW: "Particles and their properties 'exist' as independently of human intervention or observation."
So here I would prefer to say that particles and their properties can only 'exist' as potential observational events that by simple definition are dependent on the possibility of human or other sentient observation. Which is to say, any actual observable universe such as ours, requires an actual observer at its centre. With no actual observers there are only potential observable universes. And these last exist for us only as pure potentiality.