Do you experience problems with misfocusing?
The E-M10 has focus peaking, which makes manual lens focusing much easier -- this video purports to tell you how to set that up:
I have used rangefinder lenses on my u4/3 bodies quite a bit. My favorites being the Voigtländer ltm 50/1.5 Nokton and 75/2.5 Color Heliar. I also use my collection of Nikon F mount lenses. My favorite body to use with adapted lenses is the GX7. The excellent focus peaking enables precise manual focus.
I don't bother with focus peaking (E-M5) as I found it is not anymore effective than just using 7x-10x 'normal' focus assist tool (the zoomy window thingy). I link the focus assist tool to the top button for quick access.
You think the GX7 is better than the EM10 for manual focus? As it's the thing I'll mostly do.
Will get some 17 or 25 mm later on for autofocus... But not necessary just yet.