Where to go after Go? (Looking for more features and options)

I’m taking over work on a website from someone who started it with the Go theme. The more I tinker the more I realize that Go has a lot of limits. I’d love to switch to a full-site-editing theme that has a more generous set of options (borders, spacing, etc) on its blocks. The site isn’t very extensive now, so hopefully I can switch themes without creating a holy mess.

• Any suggestions on a feature-rich FSE theme, preferably free, that would be a good move from Go, hopefully without too much disruption to the content? How about Twenty-four?

• Any suggestions on how to protect myself if I try a different theme, don’t like it and want to go back to Go?

I’m a long-time techie but a WordPress newbie, so please be merciful.