OpenZFS 2.0 is a huge update for this open-source ZFS file-system implementation in that it mainlines FreeBSD support alongside Linux, there is Zstd compression support, many performance optimizations, fast clone deletion, sequential resilvering, and a lot of other improvements and new features.
With OpenZFS 2.0-RC2 and the changes over the past month it primarily amounts to bug fixes. OpenZFS 2.0-RC2 does have some minor changes around the FreeBSD support, renaming some options, a new ZFS module parameter "l2arc_mfuonly", zfs rename -r has been spun out to zfs-rename , support for zfs rename -u option to rename without remounting, and other small items. But for the most part OpenZFS 2.0-RC2 is about testing the latest fixes ahead of the OpenZFS 2.0.0 stable release.
More details on this second release candidate of OpenZFS 2.0 via GitHub . OpenZFS 2.0.0 stable is on track to happen later this calendar year.