I wouldn't describe any of that as elements of power gaming. I would call that basic social awareness, paying attention to the other players, and simply having system mastery. To be fair, I've known a lot of TTRPG players that have been lacking in those areas. But I don't think there's anything inherently bad or toxic about power gaming.
Critically, I don't think power gaming implies any system mastery or skill. A tryhard power gamer and a successful power gamer are both power gamers. Power gaming describes a player's goals in making or playing a given character. Power gaming is about intentionally making your character powerful. It's about making your character more effective. Regardless of how successful you are, that's the behavior central to the terminology. That's the behvaior and goal it describes.
Because of that, I think power gaming is inseparable from power fantasies. Even if you're just keeping up with the Joneses, if you're power gaming then you're expressing a power fantasy as best you can. On the other hand, if you're expressing system mastery without maximizing character effectiveness, that's not power gaming. It doesn't matter if you know it or not. If you're not doing it, you're not doing it.
That isn't to say that all power gamers prioritize character power so highly that it's detrimental to role play, story, and cooperation with the other characters or players or that they're foregoing sportsmanship or anything else. It's not inherently toxic. But it's inseparably about that power fantasy, even if it's just a power fantasy relative to other hypothetical characters. That means power gaming is a style of play because it will only create certain types of characters. Further, the fact that some players power gaming and other players not being interested in power gaming can cause friction and strife at the table is partly how we know it's a style of play. That's the kind of conflict that only happens when there's a mis-matched style of play.
Meanwhile, I think terms like "munchkin" are simply purely pejorative terms for power gaming or optimization. That's why they're not really used anymore. They aren't really about how I feel about my game, and are more about how I feel about your game. It's meant to villainize. But the existence of a villainous term does not mean that power gaming is virtuous. It's neither virtuous nor villainous. It's neutral, and can only be judged in terms of how the rest of the table feels. It can only be judged by how well it matches the style of play of the rest of the table.