Loading sequence of modding data:
mods\pmines\models\mlev1\*.pof overrides mods\pminesmodels\mlev1.hxm overrides hog:mlev1.htm mods\pmines\model128.oof overrides mods\pmines\pmines.hxm overrides hog:pmines.hxm
Same for all other resources. The general rule is
mod:level:single item over
mod:level:item container (e.g. hxm) over
hog:item container over
mod:single item over
mod:item container over
hog:item container
Actually to make your life easier you shouldn't mix hog and mod resources, however non d2x-xl versions can only read stuff from the hog file, so you can put d2x-xl specific stuff in the mod folder, but then you need to be careful to not accidentally add stuff there that overrides the stuff from the hog file.