In physics generally there is no "true nature". We know what elementary processes take place: scattering, pair production etc. And we can experimentally measure their likelihood. Unless we find a way to probe deeper experimentally, then that is all we can say "really" happens.Wow, great. There is a lot to read and it will take some time. But I am just curious, what really happens in the process such as in Feynman diagrams? Is the answer is that we know how physically describe the whole process, and we build mathematical tools to calculate it but we do not know its true nature?
We then construct a theory to model what we observe. This is modern particle physics, QFT etc. This theory produces complex integrals that can be expanded as a series of ever more complex terms.
In order to evaluate those terms Feynman invented a system of diagrams, essentially to make the calculations less difficult. One interpretation of those diagrams involves virtual particles.
Whether the model of virtual particle interactions is the "true nature" or only an aid to calculation is not a question physics can answer.
The Insights articles expand on this.
Personally, I believe we should remain agnostic about anything that is beyond our current ability to measure. And focus on what physics can tell us, rather than on what it can't.