This is advice if you think your employer is going to try firing you for cause so they don't need to pay a severance. When they're trying to do that your manager will try to have more face to face meetings so none of the discussions are recorded. Then they will send some e-mails to their manager with some colored description of what took place. For instance they'll say your productivity dropped or you're mismanaging your time because you didn't work on project A but in your one-on-one they explicitly told you to stop working on project A and instead focus on B. When it comes time to drop the hammer they'll have one-sided documentation of your performance.

If they're start talking about your performance definitely follow up with an e-mail about what metrics they are using to measure performance and pressure them to give you a path for correction.

If you don't have any documentation it will be easier for them to fire you and offer you nothing. If you have a bunch of documentation, especially if they know you have it, they'll be more likely to offer a severance. A wrongful termination suit will likely cost them more than your severance, especially if you have a lot of documentation of your work and performance.

Also remember HR exists to protect the company, they don't give a shit about you beyond whatever the legal requirement is for giving a shit. Don't sign anything without reading it carefully.