permalink: just postname, or custom?

This is a question about implementation; not a technical question.

For a new WP site, I’m debating the pros and cons of using a custom structure like:

Custom structure: https://mysite.com/%category%/%postname%/

My site will be posts on a variety of topics, where I will be using categories (and possibly tags) to help people narrow in on posts of particular types.

If I use the preceding permalink form, it would not work if I had multiple categories (perhaps that is where tags come in). Also, if I changed the category of a post later, then web indexing of the post would be problematic. I’m leaning toward just using the postname, for these reasons, and also to keep the urls shorter. I realize there is no right or wrong answer, but any feedback on choosing a permalink structure would be greatly appreciated.

One related question: Is there any difference/advantage to these two forms?:

Custom structure https://mysite.com/%postname%/

Post name https://mysite.com/sample-post/

Thanks.