An AGM battery is a conventional lead-acid battery (just that its acid is in paste form that is soaked into glass matting) so it is charged and has the same charging characteristics as any other battery. You're probably thinking of gel cell batteries which are totally different, rarely used in cars, and do indeed require a different charging system due to their high internal resistance that means it has to be charged at a much lower rate.
And yes, the Diehard Platinum is entirely suitable for both starting and winching duties.