Steel Ball Run's second stage starts soon and I never finished Stone Ocean. is Steel Ball Run connected to the earlier parts story-wise or is it basically its own thing I could just jump into without the backlog?
You can go in blind. Steel Ball Run (Part 7) is set in a separate continuity from Parts 1-6 — same rules (Stands exist), different history, different people wearing familiar names. Johnny Joestar is a new character who parallels Jonathan Joestar rather than being a descendant of him, and "Spin" is the part 7 equivalent of Hamon, not a continuation of it.
The connection to Stone Ocean is a fan theory, not confirmed canon: Made in Heaven resets the universe at the end of Part 6 before Emporio stops it, and a lot of people read SBR's world as "what that reset universe became." It's a good theory and Araki has never shut it down, but it's never stated outright in the text, so don't go in expecting it to be spelled out.
Net effect: zero backlog required. You'll pick up a handful of "oh, that's a callback" moments if you've seen the earlier parts later, but nothing in SBR depends on it.
