Just after the Windows 10 Mobile build 14342.1004 that released for Slow Ring Insiders, Microsoft pushed another update for Release Preview Ring, 10586.338 as a cumulative update.
As usual, this update brings only bug fixes, tweaks and performance improvements. We do not know what exactly have been changed with this update. We will keep you updated as soon as we receive the change-log.
If you notice anything new or improvements, you can tell us in the comments.