>Nuphy AFAIK doesn't have QMK compatibility, so you are somewhat limited in customization.

You mean limited in programming. They use NuPhy software for programming, not as powerful as QMK but better than Keychron K series with nothing. Therefore Halo series is better than Keychron in that matter.

Customisation is limited with Air series (low profile again but way better than Keychron low profile - you can use some 3rd party keycaps).