The VT100 and LK201 compilation switches, if 1, select keyboard handling appropriate to VT100 and LK201 keyboards, respectfully. The LK201 support has only been tested on the Rainbow.
The RAINBOW compilation switch, when set, modifies the display code to use fast video. A special routine, written in assembler, copies data from the MicroEMACS screen image directly into video RAM. This routine is guaranteed to do bad things on anything but a Rainbow. On the Rainbow, you still need to set ANSI, and you will want to set LK201.