The answer to the question that you are asking really depends on who you ask. You can achieve good practice for CSS with both frameworks, but it really comes to what you consider as a good practice.
You can find various articles on the web telling you about best practices for CSS, such as this.
I encourage you to read more about CSS and the best practices for CSS in general, then you should start to read about both frameworks in depth,
and also try both of them on some projects to really decide which one suits you better. But in the end, good practice can be achieved with both,
but you need to understand why are you using one of them. Also, have in mind that they are different paradigms and you should read about it as well Tailwind CSS vs Bootstrap:
Learn about the differences. Once you understand all of this, you will be able to tell, which is better for you and the projects that you are working on.