With regards to hiring, this is tricky because all candidates will try to put their best food forward and have a reasonable explanation for everything on their resume. In addition, low performers can look like high performers if their experience was painted by working at places with low expectations. I’ve hired very high performing people who later admitted to being PIPed many times throughout their career but these places were either greatly dysfunctional and/or just not a good fit for them.
Additionally, high/low performance has little to do with competence in the role in my experience and hiring someone truly unqualified is very rare. Some of the lowest performing people (in the long-term) were the sharpest during the interview and I still consider very bright people. Higher performers can run the gambit but a lot of companies miss out of great talent because the prospective employee fumbles over a closed book, live coding challenge.
Lower performers typically have something else going on in their life (relationship problems, housing or living situation stressors, financial stress, family stress, undiagnosed/under-addressed mental health problems, etc) and maybe during another time in their life could very well have been very high performing.
My point is, when dealing with people, it’s complicated.