I'll just leave this post here about just how large a planet can be (takeaway: depends on the core to a large extent - we could have gas giants a lot larger than Jupiter if they don't have that rocky core. Could make for a different kind of wilderness refueling).
https://medium.com/starts-with-a-bang/whats-the-largest-planet-in-the-universe-69daedc70bc9
https://medium.com/starts-with-a-bang/whats-the-largest-planet-in-the-universe-69daedc70bc9
