The OLED panel will likely be the same panel on the upcoming OLED HP Spectre x360 15. The convertible is otherwise only an internal update from last year's Yoga 730 2-in-1.
https://www.notebookcheck.net/Lenovo-Yoga-C730-2-in-1-will-have-a-4K-UHD-OLED-display-for-1650-USD.391801.0.html
Lenovo's new naming scheme has backfired and is making things a lot more confusing now.
1. Whiskey Lake
Ideapad 730S - 13" clamshell
Yoga S730 - 13" clamshell
Yoga C730 - 13" convertible
2. Kaby Lake R
Yoga 730 - 13" convertible
Yoga 730 - 15" convertible
Issue is that most users and even reviewers will refer to all of the above as "Lenovo 730"