Default [Q] [MultiROM] Performance, Partition Help

Installing roms via MultiROM does this effect performance at all? Would the rom run faster if installed normally?

Does the USB OTG read/write faster or slower than internal? Would roms have better or worse performance running off of a USB flash drive?

Also I see an option to share the kernel between roms, is there a way to do this with apps? So all apps installed are the same on all the roms, is this able to be implemented?