+1 for Ploopy mice. I have the Ploopy Adept, and I’ll never go back to another mouse. They mostly make trackballs, but they do have a “regular” mouse if trackballs aren’t your thing.
The biggest problem with Ploopy is that they only seem to make mice for people with bigger hands, so if that’s not you, you’re kind of screwed :/
I have the ZSA Moonlander and Voyager keyboards. I like them a lot.
I also have the Ploopy Adept and Nano mice that also run QMK.
I bought all of them preassembled. I’d love to know what other brands are out there that sell preassembled peripherals that can run open firmware.