During the First Battle of Kamino, we see Alpha-class ARC troopers.
The group of 100 Advanced Recon Commandos known as the Alpha-class Advanced Recon Commandos, also known as Alpha ARCS or Alphas, were created by the Kaminoans of Kamino using the DNA of Jango Fett. These ARCs would serve the Republic as members of the Grand Army's Special Operations Brigade.
The development of the Alpha-class ARC troopers took place after the growth of the Null-class Advanced Recon Commandos, whose existence was a secret closely guarded by the Kaminoans. The production of the Alpha ARCs was greatly refined with the help of the lessons learned during the creation of the Null ARCs.
The Kaminoans trained and grew the Alpha ARCs under Jango's direct instruction, but they were unaware that Fett had the ability to put his own personal orders in all of them. One such order was that they should destroy all of the younger clones if Kamino were to ever fall into the hands of the Confederacy of Independent Systems. During the First Battle of Kamino, Alpha-17 almost carried out this order, but the Galactic Republic was able to defend the planet.
The Alpha-class ARCs were created with unaltered independent minds, much like the Null-class that came before them. However, Jango instructed the Alpha-class ARCs to follow the orders of the Jedi, which made these second generation ARCs more obedient and reliable to them. However, the ARCs were still able to voice their disagreements or even their opinion of a Jedi's order if they thought it was incompetent or lacked strategy.
During the Clone Wars, there was also a tense rivalry between the Null-class and Alpha-class ARCs. While the Alpha-ARCs naturally inherited Jango's solitary nature, they were proud to be a part of a great military force. They also had respect for the fighting and leadership skills that the Jedi showed. The Alpha ARCs saw the Nulls' open disregard for Jedi and Republic authority as an insult to the entire clone army. The majority of Alpha ARCs were only loyal to the Galactic Republic and followed the Jedi's leadership to some extent, but the Null ARCs only swore their loyalty to Kal Skirata. The Alpha ARC troopers, therefore, considered the Nulls to be renegade clones who were a disgrace to Jango Fett's legacy.
When Supreme Chancellor Palpatine initiated Order 66, not all of the Alpha ARCs followed it. While some chose to obey the Chancellor's order, many others chose to disobey Palpatine because of their unaltered independent minds and the close relationships they had with the Jedi during the Clone Wars. Some Alpha-class ARC troopers retired to Coruscant or Kamino and became instructors at the Empire's recruitment camps. Others followed in Jango Fett's footsteps and became bounty hunters. Some even joined the Alliance to Restore the Republic.