Options: (From top layer to bottom)

Layer 15: Seems to be a grain effect. I disable it.

Mouth options: 
mthOpen_pantInside: Makes the mouth more circular, should work with any other option.
mthOpen_cumInside: Cum in mouth while frontGuy is still there. Enable the copies for a brighter cum.

"blur" guys: No options. All the cool layers in the original were in the regular non-blur guys.

frontGuy2:
noCum: Enable LAnoCum and manNoCum, disable the others if you don't want any fluids.

frontGuy:
Default: Enable rika, fix, an LA of your choice, and manNoCum. Make sure the mthOpen group below frontGuy is disabled.
Smile: Smile with frontGuy. Enable smile or smilesmallmouth in mthOpenSmile and another LA of your choice in frontGuy.
Small Mouth: Disable rika and enable the small mouth option of your choice, and enable mthOpen group.

OL: Adds light particles and brightness.

mthOpen_pant and mthOpen_cum: Options for when not using frontGuy.

mthOpen/mthClosed Groups: Opens or closes Rika's mouth. May need to be enabled/disabled for other options to work.

Clothing: Self-explanatory. In leggings, enable the fixes for solo/backGuy/smallboobs if needed.
I changed the shirt to blue pretty early on, because I hated the pink color (why the file is called rikaBlueShirt)
Looking back, I should have made a copy of it... but it shouldn't be too hard to change back or copy from the original.

backGuy: No options added by me (yet).

Eyes: Enable either eyesHalf or eyesFull, not both.
SL/SLless change the reflection in Rika's eyes.
furtherUp raises Rika's eye.
left/right eyebrows allow you to individually move each eyebrow. 
You can mix eyebrows from half/full by disabling everything but the eyebrows in one, and enabling everything else in the other.
hairFront allows you to put the original eyebrows and eyes partially behind the hair 
(you can sort of replace this effect by changing the opacity of the individual eyebrow layers)
eyesLA is the outlines for just the eyes.
lashOpen/lashHalf is the original outline, has eyebrows and eyes all in one. Different eyebrows in half/full eyes.


Small boobs:
Ink: Disable body. Enable smallboobsbody, smallboobsbody2, left nip and right nip.
clr: Disable lightfur, fur, and the rim on the bottom. Enable smallboobsfur, lightfursmallboobs. 
Reverse to reset to normal boobs.

A bunch of lighting and background settings: Play around with them.