The models you can enable/disable with the options are the Luclin models. However, editing the options does not work for P99, they are hard-coded disabled*. To enable them, you'll need to follow
this guide.
To enable the Velious armor skins, you'll need to replace some files per
this guide. It will basically replace classic leather/chain/plate with Velious leather/chain plate, so you will not have ANY classic armors at all (except possibly helmets, I don't think this change affects helmets).
*This does not apply to elementals, they still need to be turned off via the Everquest options.