I am just curious about what is specifically defined as no buffs. Is it just playing without ISO-8 crystals and the hexagon thing or is there a specific team bonus that is banned?

As defined by the category rules, No Buffs runs have the following restrictions:

-Beat the story from New Game -You cannot use ISO-8's -You cannot use XP Cubes -You cannot use the Alliance Enhancement -You cannot level up skills. -Health and Energy pickups are legal

There is no restriction on team synergies, especially since the starting team already synergizes with itself when starting a new save.