For finding your persona you need to stick on your audience, it depends on you working on which industry, who is you main users, you are B2C or B2B or etc? By listing these data you will categorise them into the more detailed table and at the end.

There is many way to managing a project as you know, fourtantly the products like Figma bring the useful tools for management on design and the products like Trello and Slack bring more strategy and tracking tools. So we used to schedule consistent sessions with client to be sure we are on the same line.

Yes, depend on the project we deliver Design system which included UI kit.