For the most part, it depends on your work flow. Just about everyone I know has a basic work flow of: animating in blender (others may use Maya), and exporting to something like FBX, which you then load into unity. Thats assuming you mean 3D models.
Are you starting with sex animations, thus starting with 3D relatively knew, or have you been working with models already.
I ask because the main pain in the but with this kind of 'work flow' is its not just simply what tools you use. Its also how you design and use the character models. For example, a lot of the effects you may want to do (effects specific to sex animations) may require you to add 'features' to your character's rig that will require you to redo previous work (walk animations) if you want to use the same model and have all the data still be compatible.
My work flow, when animating a 3d character for a game (not that I actually do this regularly nor profesionally) is that I actually have 3 rigs. A complex rig, a control rig, and a game rig. Basically the control rig is 'simple' and controls the complex rig, the complex rig includes lots of math and nuances to allow me to control things in specific an automatic ways (such as have a character automatically ballance themselves), then theres a bit of math that reduces the 'complex rig' into just a 'game rig' that still captures what I want, but only contains the basic rig and raw animation, no helpful bones.
When it comes to the high quality sex animations, often a lot of the complexity is made easier in blender using bones to control either other bones, or other effects (a bone representing scale can be used to animate the opening of an orifice). However, a lot of blender's power (or maya's) gets lost when you want to port things over to unity because unity wants to work with simpler stuff, and getting similar functionality or power to that of blender or maya (such as animating simple drivers to control other effects) is difficult an almost always requires programming. programming isn't the worse, but its trynig to keep uptodate with unity's api changes that kills me, since I'm very slow with worknig on projects.
Often its easy to just bake every detail you want in an animation. So things like jiggle effects and distortions are easier to back into an animation using shape keys/blend keys. You could dynamically animate them with the character rig, lots of game do this, but 1 you get a complicated rig that makes it a pain to animate and export, and 2 you have to set up a technical rig and get something coded pretty sophisicated, and you probably don't want to spend 2 months of tech work just so you can have dynamic jiggle physics in unity, before you even have animated anything yet. Hense easier to just bake effects into the animations. but even then, the issue is 'work flow' is the character rig read for certain effects to be easy to animate, and can it be baked? high quality animations use lots of bones, and if you get characters from something like smut base, they will have more bones than unity would like, its teadious to animate them all (which is why I automate my rigs with lots of math, that I can only do this using 'drivers' in blender), and there's not a good way to bake it into the animation. Which is why I often have to know the technical issues before hand and then create a custom rig from scratch that solves a lot of the baking issue. but its been a good while since I've had to deal with that since I've been doing a 2D exploration for a while.
