Some highlights that touch on your questions:
Four PFAAs have been found in rainwater, which means they are ubiquitous in all water supplies. Whether or not they are above the safe level threshold is another question pertinent to particular source.
They are nanoparticles so typical backcountry filters will not remove them. Since they are present in rainwater, I'm not sure how effective distilling would be
The article mentions nanofiltration and reverse osmosis. The only thing mentioned that you might find in the backcountry is granular activated carbon (GAC). GAC is good stuff and underutilized in the backcountry IMO. The problem is effectiveness of GAC is hard to guarantee, because it is a function of how much it has been used and how contaminated the source is.
We are probably too early in the process to fully know the health implications. It is concerning to me that as people are studying PFAs the recommended safe levels are being reduced.