Genymotion is a fast emulator for android which can be used for development or for other android usage if you know the tricks of the trade!
Gm emulator uses android AOSP image & runs on virtual box using virtualisation. Since it uses visualisation it could use hardware acceleration features of the CPU and the genymotion AOSP images are optimised for the same, hence genymotion emulators are the fastest emulator for android i.e until android studio 2.0. Though latest android studio emulators work on similar fashion; which one of them is faster depends upon your use case. Anyways, flashing Google PlayStore on android studio emulator is more tricker.
To flash files for rooting, Xposed etc. in Android you will be needing a custom recovery image, it allows us for flashing system level files which wouldn’t be possible otherwise.
There are different types of custom recovery images such as Team Win Recovery Project (TWRP), Clock Work Mod, CyanogenMod Recovery, PhilZ Touch. In general, these recovery images are to be flashed permanently to your device [Of-course you can remove them & flash stock recovery] .