It is currently having the build approved on Steam. I expect it to be up before the end of the year <3 Ty for your patience.
The steam build will be the full/paid version of the game, including all routes. Other than that, no it’s no different other than Steam achievements 💖
As for Criminally Yours it is now currently available on Steam! https://store.steampowered.com/app/3790640/Criminally_Yours/
The $2 version here and the $5.99 game on Steam are the same version. It costs money to put the game on Steam, so for the inconvenience, I made the game over half off on Itch permanently. I'd only recommend purchasing on Steam if you want acheivements and/or to support us directly, regardless, it's at your discretion.