The author of VcXsrv himself answered part of this question here.
Currently the default font path is
fonts/misc/,fonts/TTF/,fonts/OTF,fonts/Type1/,fonts/100dpi/,fonts/75dpi/,fonts/cyrillic/,fonts/Speedo/,built-ins
When you want to add an extra one, you should add it to this list and pass
it on the command line with the -fp option:
-fp fonts/terminus-font/,fonts/misc/,fonts/TTF/,fonts/OTF,fonts/Type1/,fonts/100dpi/,fonts/75dpi/,fonts/cyrillic/,fonts/Speedo/,built-ins
The specified directories are relative to the directory where vcxsrv.exe is
(default C:\Program Files\vcxsrv)
You can also add the directory to the font path with the xset +fp command:
xset +fp fonts/terminus-font
For using Windows 10 fonts, it might need a few more steps. The main steps of Xming to create fonts.scale and fonts.dir are still valid. When starting VcXsrv you should follow marha’s instructions in his answer and add C:/Windows/Fonts, within the -fp argument list. (Notice that you must use forward slash / instead of backward slash \ in the path.)
If this still doesn’t work, try Cygwin/X. The performance is not as good as VcXsrv but it works well. Most of all, all the X tools are compatible to VcXsrv. You can use a lot of X command line tools (like xset +fp ...) to configure VcXsrv after it has started.