Letters of recommendation from which employers?

I’m between asking two employers for letters. My current job I’ve been at for just over a year. My boss is a very negative person and I don’t think that she would write a very strong letter for me. Is it okay to have a letter from a coworker? Someone from an adjacent team who I work with often? Additionally, I’ve had a side job at a bar for four years. Would it be worth anything to get a letter from my manager there? I think that they could really speak to my work ethic and ambition, but I know that it’s not a super professional gig. Which would be stronger?

Secondary question: I graduated undergrad in 2020 and masters in 2021. I went to a very large school for both and was not particularly close with any of my professors. I’m still going to reach out to a couple of them and hope that one says yes. Any tips on how to ask when you’ve been out of college for a few years?

Thanks in advance!