Cowtastic Cafe is hands-down my favorite BE game. It’s not the longest game, clocking in at about 30 minutes a playthrough, but the sprites, growth sequence, and actual gameplay are all top-notch.
Research Station M-00 is another good BE game I’d recommend giving a go. It’s got other body part expansions, as well, but BE is the main focus.
I’ll also toss Fetish Master out there, although it’s definitely fading with age. It primarily uses text descriptions and a hodgepodge assortment of pictures, and it’s not BE focused (although it’s basically a sandbox, so you can just focus all your attention on BE aspects), but there’s no ceiling to growth, so if you want extreme BE, it might be worth a look. I will note that I personally had to go in and homebrew a few coding lines to tweak it to where I liked it, but you don’t have to do that, and you could use the Dev mode to cheat a bit, if you just want to skip the ‘story’ bit (and I use that loosely).