Way late to the game on this one. I've done a M200 conversion, sharing my config.g as I haven't had the time to read through all 99 posts on this thread (trying to finish an M300 mod by next weekend for MakerFaire PDX). Welcome any input if I've done something wrong. Hope it helps if you're having troubles.
I swapped hotend to a Slice Engineering Mosquito keeping the extruder, added a BLtouch for leveling and z-stop, removed the waffle board and added PEI (Buildtak Flexplate is going on it today).
Tinkerz