The companions appearance changing when they have armor on.
Some installer options are actually sfall or HiRes options. Just open
ddraw.ini or
f2_res.ini and change what you want.
To disable armor appearance mod open ddraw.ini and change
EnableHeroAppearanceMod value to 0.
That's for the player's appearance, not companions. If you want them to not change appearance, you'll have to reinstall the RP. Just uninstall the RP and then reinstall choosing the options you want.
EDIT: To those asking about the next release, well, let's just say I hear sleigh bells approaching.