After seeing Jeremy Keith mention that he was testing Safari 15 via the Safari Technology Preview, I decided to try it as well. I'm writing this post in it right now and I plan on using it for a few days at the very least.
One thing I noticed right off the bat was that the Safari Technology Preview didn't import my Safari settings. It did keep my history in tact though. So I'm jotting down my settings to make it easier for me to remember - perhaps you can use them as well.
- General tab