My workstations are Debian, my laptops are a mix of Debian and Arch, same with test hardware.

They all look the same - KDE as my desktop environment, no generic software added at install, just adding what I want. If you were to use any one of them purely from the GUI (KDE), I doubt you’d know which was which without checking version info.

Linux is a kernel. A desktop environment is the GUI. The distro is packaging.

The difference between distributions is predominantly what is packaged up, the tool used to install/update, and an overarching philosophy on those tools.

Debian is about being stable. This means more dated packages, but running into issues from an update is (mostly) not even a question when running the stable branch. Amazing for workstations and older hardware IMO.

Arch updates constantly. Updates can introduce breaking changes, even minor ones, which can interrupt workflow. It also means the latest and greatest features are right there and ready quickly. I like arch for testing and making use of recent hardware that may not have support elsewhere yet.

You could also build entirely from source, use a downstream from Debian like Mint (Debian Edition) or Kubuntu, or downstream of Arch like SteamOS or EndeavourOS. Downstream distributions add more opinion under a more particular approach to their upstream counterparts. For some its to make the system easier to install (EndeavourOS vs Arch), add more recent features (Kubuntu vs Debian), or to make something incredibly specialized (SteamOS, formerly based on Debian and now based in Arch, highly focused on gaming).

The only thing thats “pure” Linux is the kernel. Everything else comes down to purpose and preference.