One question: Does being put on a PIP disqualify you from unemployment benefits if you get fired for not passing the PIP?
Unemployment benefits are strictly a function of being let go for cause or not for cause. You might be on a PIP for cause-related reasons (absenteeism, showing up drunk but otherwise contributing), or non-cause-related reasons (the maladroit who took over as your manager got told to he needed to downsize his team). The presence of a "PIP" is unimportant. What is important is the documentary burden employers have to meet to disqualify you for unemployment, which in California can be substantial.
Even if they have a really good reason for firing you for cause, you might still get your full unemployment if they deem it less expensive than fighting with you and the state over it.