Can you Transmog Legion artifacts? Want to transmog my Artifact
Just like any other weapon you can transmog your artifact into something else at the transmogrifier. To apply a tint to your artifact instead, you will have to visit the Artifact Weapon Forge in your Legion Class Order Hall.
Can you still unlock Legion artifact appearances? Yes you can. All artifiact appearances are still available except for Mage Tower challenges. The latter ones were meant to be a solo challenge to unlock a cosmetic and would be trivialized by level 120 characters.
Can you Transmog other classes artifacts? Different Artifacts at the same time
With these new rules, you are able to transmog any artifact appearance from your class, as long as it follows normal weapon transmog rules (i.e. 1-hand to 1-hand, 2-hand to 2-hand, etc).
How do you unlock warlock artifact appearances?