We reported after exploring Build 14327 a bit that the Insider Preview Ring selector is now available on the Update & Security settings page similar to what we have seen in case of Windows 10 on PC. The Ring selector has a slider to let you choose Rings based on your Risk-affinity. Till now it was not sure whether it was functional as Microsoft didn’t report about it official changelog. But Microsoft has now confirmed that Windows Insider app is not needed for the Build 14327 and higher and this Ring selector is functional.
Windows Insider Program settings page: We have moved the Windows Insider Program settings to its own settings page. This is where you can go to join the Windows Insider Program (or stop receiving Insider Preview builds) and adjust which ring you are in. On Mobile – for Build 14327 and higher, the Windows Insider app is no longer required. To get to this new page, go to Settings > Update & security > Windows Insider Program.