What is current best OS and desktop

[ryo]

I think manjaro is arch spinoff.

Technically, you're not wrong.
However, a distro based off something else doesn't necessarily make it better, worse, or the same.
On the desktop, Manjaro is a fork of Arch, it was initially designed to be a simpler way of installing an Arch-based system with properly tested software and additional tools to make it easier to use for the less tech savvy Linux user.
But over time Manjaro evolved into becoming its own thing that just happens to be based off Arch.

And on phones, both Manjaro and Arch-ARM got developed in isolation from each other.
Manjaro just used what they already had for desktops, and slapped megi's kernel, ARM repo, and 3 mobile DEs on top.
Arch-ARM on the other hand is an unofficial fork of Arch itself maintained by an independent Arch user.
So Manjaro effectively has nothing Arch-ARM has and vice versa, but both do have what Arch has.