If anyone is still has yet to write their UC PIQs, I would suggest getting them done sooner rather than later. I had to rewrite some of mine recently because I figured out a big mistake I was making when writing these essays. A 350 word limit can sometimes make you want to fit in all of your achievements before you run our of words but after reviewing a lot of exemplary essays from websites and some of my UCLA friends' essays, I realized I had been going about it the wrong way.
This may not apply to all cases but a general theme among the top tier essays written for UCs is that they tell a story to some extent.
This website has some great examples about what I am talking about. Even the prompt about leadership experience is shaped into a story.
Obviously telling a story is easier said than done but: https://blog.prepscholar.com/uc-personal-statement-application-essay is better if you are looking more for elements of a good essay rather than examples.
Another good place to look is the UC website itself. This link takes you to the UC website's PIQ section for transfer students where they give insight into things THEY look for when they are reading your essays. https://admission.universityofcalifornia.edu/how-to-apply/applying-as-a-transfer/personal-insight-questions.html
These are just some of many websites you can utilize. There are countless examples of outstanding PIQs. I might not be the best essay writer in the world but If I do know how to write a bad essay from experience. The best advice I can give you to not write your essays like I did a year ago is to get them reviewed. Your professors, your parents, campus faculty, your neighbor, your friends, even your dog. Get the reviewed by 2 to 3 people to avoid information overload. This step is something I missed out on my first year of writing application essays and I paid the price. The best commentary could come from the most unexpected sources. My friends were the ones who told me about how wrong I was writing these essays. Stay motivated guys fall semester is nearly complete. Good luck and happy writing!