Rigify and rigging in general
Rigify’s rig generation system works on a module system. Each provided metarig from Rigify are in fact a bunch of modules put together as an example. You are free to add, remove, or even make new modules as you like. If you don’t need the facial module, delete it from the metarig and generate the rig as is. Or if you need only parts of it, generate the rig with the facial module, and then delete the unneeded parts in the final rig.
But, that’s the kind of things you should always plan and do before the skinning stage, to avoid cornering yourself into revision hell.
Now that you are in the case of having to modifiy your rig after skinning, it really all depends on what you want to remove from the skin. If you want to remove all facial features, it’s really as simple as removing the facial modules from the metarig, re-generating it, and then bind the whole face to the head bone and delete all legacy facial weights. But if it’s more granular than that, it really depends on what you precisely need to do. But since Rigify’s facial module is somewhat simple and easy to “ignore” if you don’t need it, I would first wonder if it’s worth the trouble if I were you.
I highly recommend you to check Rigify - Blender 4.1 Manual if you want to know more about how to use Rigify at its best.
If you want to know more about bespoke rigging, or simply general tips about rigging and even animation, I highly recommend watching Pierrick Picaut - YouTube. That dude made a lot of very comprehensive guides that explain both how to do things, and more importantly, why.
There can be many ways to answer your needs, but while tools like Rigify are more aimed at giving general answers to most questions and can be somewhat customized to specific needs, at the end of the day it’s hard to tell exactly what to do without the specifics of the situation.
So don’t hesitate to tell us more about your situation, you can even upload your file if you want (just don’t forget to remove unneeded things and use Save As > Enable Compress option so it’s lightweight and nice to share).
Deform rig, channels and exporting
When it comes to exporting to a game engine (GE), you are not supposed to export the whole rig. The GE only cares about the final deform that actually deforms the meshes.
Only the deform bones are needed for export. But all the rest of the rig isn’t useless, it is for you, the animator, who needs visually-appealing and easy-to-use controllers, IK systems, eye targets, space switchers and whatever fancy thing animators like to have in order to do their job more efficiently. You shouldn’t delete the rest of the rig either (unless its limbs you don’t animate at all, but that’s what I mention above).
In addition to exporting only the deformation rig, you should also bake the animation on it. For two reasons: depending on how the rig is made, the animation keyframes are often not on the deformation rig itself, but on controllers or other intermediate bones. Plus the def bones are partially influenced by other bones. Exporting the def rig as is would result in a broken animation.
In addition to that, every frame should be keyed in your animation software. Because every non-keyed frame will be left to the imagination of the GE. Which will already compress the animation data, interpolate, all that using possibly different interpolation methods, different rotation orders on your bones, which leads to interpolated frames looking somewhat different from the animation software, if not broken.
Hence, all you should ever do to export a rig is bake the animation onto the deform bones and export them.
Some exporters like FBX have an option to export only deform bones, with animation baking. Do that. It’s the simplest thing to do.
For the few exporters that don’t offer that as an option, you can always try to save your animation in a different file, from there select only the deform bones (they are in their own layer in Rigify’s rigs), bake the action with clear parents/constraints, and then delete any other bones and export.
It’s the manual and annoying way to do it, you are only baking and deleting thing at the time of exporting, and you should then go back to your full-featured rig. But since you export for Unity: just use the FBX exporter x)
Now on a very different note, I feel the need to go a little bit off-topic and talk about words like these:
Maybe you know things we don’t. Maybe you are just young in your learning process. Maybe it’s just unfortunate words that came out wrong. I don’t know. I like to think it’s the latter, considering your latest message. That’s why I focused my post on answering the problems at hand in priority.
But maybe be a bit more careful and humble in your words. It can lift a few eyebrows when you read someone criticizing tools and telling developers what they should do 
And yes! Generally for a game actor you’ll want to bake down your deform bones’ animations for each action and delete everything else/export with only deform bones (or depending on your plans any other controller you expect to reference directly in your game engine).