In other words, is Order 66 a clone-only thing or do any Jedi slain by anyone ordered/sanctioned/hired by Palpatine and his Empire to do so qualify as part of Order 66?
Order 66 was a subconsious order planted into the brain of all clones via a control chip which is hinted on in the last season of The Clone Wars.
Anakin/Darth Vader was never part of order 66 itself. Palpatine/Dath Sidious triggered order 66 out of several reasons:
- The war was almost at his orchestrated end.
- He had gained most of the legislative and executive power in the galaxy by the implementation martial law.
- He was exposed to the Jedi. Even if the Jedi that were at his room were now dead, someone would find the bodies of at least Mace Windu that dropped down to street level and that would raise some questions.
- Anakin was finally willing to accept him as his new master out of fear of losing Padme. This was clearly shown to Palpatine by Anakin attacking Windu which lead to the afore mentioned incident.
So for once, Sidious had reached his most of his goals. The only thing left was to dispose of the only force that could probably put an end to his reign. While Vader now played a part in the Jedi purge since he was obviously loyal to Palpatine now, he was not killing on part of Order 66 but out of his own motives.
Thus the murders he commited as now Darth Vader can be attributed to Palpatines overall strategy but not to order 66 itself as it was never done via the control chip but out of fear of losing Padme.
The killing of Jedi by Vader is part of the Great Jedi Purge, not Order 66. Order 66 was an order given to the Grand Army of the Republic to execute the Jedi through an inhibitor chip implanted in each soldier's brain. The order's intent was to execute rogue Jedi, not for a mass genocide of Jedi, but the order was nevertheless used for that purpose.