Hi there, and welcome to Android Forums!
I used Chomp for a long time, and the Darling Bride still does on her S8 Plus. However, I told myself when I got my Note 8 I would give Bixby a good, honest try. So I use the stock messaging app.
There are good things about it like Bixby integration ("Hi Bixby: open camera, take a selfie and send it to _______ in Messages"); and challenges (no dark mode). But I fixed dark mode by using a completely black image as the background image - you can use any image. So if you want to give Bixby a try, and it's really good with complex commands, I can suggest the stock Samsung Messages app. Otherwise, it's hard to go wrong with Chomp.