>>8653582
Also as someone who does Koi and AI, I think AI is nice for getting ideas, being it poses or clothes and such... If I want to do create something myself though (and not being limited by if the AI get's what I want + randomness of what it does), Koi can be a really nice creative outlet.
As the others already said, it's mostly something to create your own character in and then make stuff with them. Though I know for the "simple users" it's just a get-card-of-current-fotm-and-throw-it-in-free-h simulator. As mentioned, Free H has preset sex poses, but it's not very customizable and might look weird depending if the cards you're using are smaller sized then the preset animations are made for...

>>8653701
>>8653709
In contrast, doing things in studio yourself allows you to have much more freedom, but it does take quite some effort to get into I guess... You can make sfw scenes like comics or all day stuff like others said, or you can pose your own sex scenes, which allow for all kinds of posibilities. For advanced users, you can also start animating yourself with keyframes to make stuff like this: https://files.catbox.moe/q5w4fp.webm

I guess in the end it depends on you... Are you the more creative type or do you just want a quick and easy thing...