The Jedi would be the most directly affected. They wouldn't be massacred, and their order could continue to thrive. Also, the clones would be affected as they wouldn't have to carry out the unjust order. And of course, Anakin himself would be on a different path, likely seen as a hero rather than a villain. Padmé might also be affected as she wouldn't have to witness Anakin's fall to the dark side.
Well, if Anakin stops Order 66 in the fanfic, it would mean that the Clone Troopers wouldn't turn on the Jedi. Anakin might have a change of heart after realizing the full implications of what Palpatine was asking him to do. He could then warn the Jedi Council. This would completely change the course of the Star Wars saga. The relationship between the Jedi, the clones, and the Republic would be very different, and there would be a whole new set of stories to tell about their future together.
Well, in the fanfic, Anakin's skills would be a huge asset or a threat to the First Order. If he decides to join them, his combat abilities and knowledge of the Force could make the First Order even more powerful. However, if he realizes that they are on a wrong path, like the Sith - influenced path he once walked, he might use his skills to undermine the First Order from within. He could start by influencing the stormtroopers, showing them that there are other ways than blind obedience.
Well, he could either try to take over the First Order with his powerful Force abilities. Maybe he would see it as a new tool to gain more power and control in the galaxy.
Some in the First Order could see him as an opportunity. They might think that his skills and knowledge could be used to strengthen their military might. However, others could be suspicious, especially those who are power - hungry themselves and see Anakin as a rival for leadership within the organization.
The First Order's higher - ups, like General Hux, would likely be suspicious of Anakin. They wouldn't want someone with so much power and an unknown agenda running around. They might try to keep an eye on him, or even plot to get rid of him if they think he's going to disrupt their plans for galactic domination.
Younglings who were disillusioned with the old Jedi ways might be attracted to Anakin's new order. They could see it as a chance for a fresh start and a different approach to using the Force.
The new order Anakin creates could be centered around family. Since Anakin's love for his family was a strong driving force in his life, the order might place great importance on the bonds between its members. It could also have a more inclusive approach, accepting those who were rejected by the old Jedi Order due to their backgrounds or past mistakes.
There could be a hermit or an outcast Jedi or Sith on Dathomir. Anakin meeting this character could lead to a great revelation. Maybe this character has been in hiding on Dathomir for years, observing the balance of the Force there, and Anakin's arrival disrupts that balance and forces an interaction that changes Anakin's perspective on many things.
One great Ahsoka and Anakin fanfic is 'The Apprentice's Journey'. It delves into their relationship during their time as master and apprentice. It shows Anakin's complex emotions towards Ahsoka, his pride in her growth as a Jedi, and also his protective instincts. The story is filled with action scenes that they face together, and the character development is really well - done.