This thread is trying to answer question "Do fixtures lessen cpu resources?"
Each test requests what it needs, and the fixtures take care of setting up and tearing down those dependencies, so tests don't have to rely on dependencies which were set up (for example) by a test.beforeAll and are less likely the re-use resources. So that's the isolation.
Honestly the isolation is not perfect though, because stuff we put into databases doesn't magically disappear. We do however start with a fresh browser context.
Now I realize that you were not just comparing page objects by fixtures, I have to admit that fixtures will take a bit more resources if you previously used a test.beforeAll and now want each test to do its own setup, possibly repeating some things which were already done for a previous test.
Rayrun is a community for QA engineers. I am constantly looking for new ways to add value to people learning Playwright and other browser automation frameworks. If you have feedback, email [email protected].