Who had the most impact on the series?

Yes, he learns the magic from them but he needs the Keyblade to be able to use the spells.
I or someone can prove this by playing KH at the part when Sora receives the Wooden Sword again from Riku, if he can use magic with the Wooden Sword, then I have been proven wrong.

 

He could. Look at the video at 08:46. Sora used Firaga with his toy sword.
YouTube - KH Final Mix - Walkthrough (47) - Hollow Bastion (Pt. 1)

 

That video is proof that Sora can use magic with the wooden sword, maybe it shows that Sora had magic powers before he recieved the keyblade but is hasn't been awaken yet. As the keyblade is the weapon of the heart, so it created by magic and hadn't shown up until Sora was in trouble.

 

Mickey didn't even fight against the heartless. He didn't even bother trying to fight against them, so that don't count.

 

yeah, all he did was shake ur hand

 

Okay, running away also counted?

 

talking bout timeless river mick

 

Was the Mickey in Timeless River the Keyblade Bearing Mickey or was it the past Mickey like the past Pete? Or is it unknown?

 

Its same as the keyblade bearing mickey. Since if you steal the cornerstone of light, it changed their future.

 

that is true but if that happen there would be no story with King Mickey which equals no story with DSora and group

 

that is true but if that happen there would be no story with King Mickey which equals no story with DSora and group

 

it is the past mick cause remember during the credits u c A mickey runnning 2 catch the boat.
they dont tell u which mick it is 4 suspense or mystery or something like that, u figure it out during the credits tho

 

But, what they do in Timeless River could change the future right?

 

right, but in the end, nothing changed.