[my definitions of various playstyle terms]
What you described as "minmaxing" is sound closer to the "optimizing" description then the actual minmaxing.
Minmaxing can also be, and usually, used in a wider sense, of gameplay that focused not only on maxing your attributes/gear/abilities, but also
making all of your in game decisions, including whole character creation, based on the mechanical aspect of the game, with no actual attention given to the roleplay, lore and narrative, or it is build based on the mechanics.
That doesn't necessarily imply that they have any "weaknesses", they could have equal number in every stat, if that make them objectively stronger overall. The weaknesses that can occur from minmaxing, its just the game rules trying to shut down that kind of behavior, but it not always works. And Powergaming implying the gameplay where player trying to get more powerful, no matter if that doesn't make sense from the story/roleplay perspective, or it is against sportsmanship towards the other players, and minmaxing as you said could be a part of powergaming, but powergaming is more abstract and wider therm. For example character who making all of his moral decisions on his powergain instead of his character morals
Imho the first three, from the top, should be strictly banned from any good dnd campaign, and, at least, not a main development focus in a video game that based on dnd, as it often happens, especially with the mmo's
