Which "stable" Rom version are you using on mi2/mi2s?
Further question: which zip file did you use to install the xposed framework?
Did you use the Framework for 32-bit processors: xposed-v74-sdk21-arm-MIUI-edition-by-SolarWarez-20151008.zip ?
At least the version of twrp I know does NOT allow me to choose the system or to switch to the other system.
That's the main reason why I still prefer cwm because in case of a newly installed system not booting I can still switch back to the other system.
Or does anybody know a solution for...
Check this
http://en.miui.com/thread-102413-1-1.html
And if you want to have cwm you might need to keep on that MIUI version until a solution is found.
Drawback is that since 5.4.24 custom recoveries are not longer booting, the workaround from 2 weeks back no longer works.
The MIUI developers have changed the bootloader again ...............