Particles with similar arrangement will be seen or felt as same. Whereas particle with different arrangement will be seen or felt different.
But we don't see everything e.g. air which are still made up particles. It's because, our eyes which itself made up of particles receive the photons or particles and brain which is again made up particles has developed a mechanism to only see photon particles of visible spectrum (i.e seeing only a particular type of arrangement). Leaving that arrangement we cannot see anything.
But how can brain made up of particles can only see photon particles arrangement. It is because arrangement of particles in our brain i.e receptors. As we all know a particular arrangement only fits with another particular arrangement just like lock and key. But it can be erroneous to some extent, same as we can make duplicate keys which are not exactly the same (i.e. remains within the error range).
Is free will related to degree of error we make? Can we change our reality?
I think yes, because we are free to choose the amount of error. We/particles are free to choose both 8 and 9 in the above diagram even though they are not same. So you can say it either 8 or 9, that depends upon you, and choosing is random.