Chrys, in Tales, it does say about Fett's quote about Justice being the greastest good, while standing trial was spoken by "Jaster Mereel, who would later be kwown as Boba Fett." However, because of the all the prequels and the Open Seasons story, it is believed now that Boba used Jaster's name as an alias sometimes, and that it was an alias while a Journeyman Protector on Concord Dawn. Kind of an "out of respect" kind of thing. That way all the books can still be used and considered part of Fett's history.
As for the Mandalorians during the Clone Wars, the renegade ARC Trooper, Spar, reorganized the Mandalorian Protectors (who had Tobi Dala and Fenn Shysa in their ranks) and fought on the side of the Separatists. They referred to him as the "son of Jango Fett," which explains the Marvel comics story of why Tobi and Fenn thought he was Boba. Something which Spar didn't discourage, apparently and it got him killed by Ailyn Vel later on in life.
By the time of ANH, the Empire still used clones, they just had more than one facility, and used many different clone donor's. Usually from high ranking families. This way one facility couldn't be targeted and cripple the Empire's strength. They also augmented their forces, though, with regular enlistee's. Making it a mixed group of clones and regular humans.
--Sadriel Fett (BFFC Moderator)
"I'm just a simple Fan, trying to make my way in the universe."