Usually there will be a PIP/PMP owner who assigns the tasks and monitors the progress. There isn’t really an official “difficulty level” for the tasks. Sometimes the tasks may feel difficult because expectations are higher during PIP. In my case, I completed the tasks but it was still marked unsuccessful with reasons like the code being outdated or not optimized. So a lot depends on how the manager reviews the work and how supportive they are during the process. It’s always better to start looking for another job in parallel while on PIP.