Not to state the obvious, but you should just be doing whatever is most effective. "Playstyles" are a way of describing the overall nature of the preferences in the way one chooses which actions to preform, rather than actual "things" in themselves, and therefore trying to pursue a specific playstyle is glossing over the reason the playstyle exists in the first place.
Trying to imitate playstyles directly is detrimental. At a low level this is especially true because you really don't understand the reasoning behind the decisions that other players make. Using a lot of aerials isn't good; the way that Mango uses them is good. Grabbing a lot isn't good; the way Mew2King uses grabs is good.
unpredictable fsmashes like Mang0's marth?
What makes those F-smashes unpredictable? What makes them good in the situations that Mango is using them? I guarantee that Mango's decision-making process behind when to throw out a seemingly randy F-smash (and the way the rest of his actions complement that decision) is vastly better thought out than a superficially similar F-smash by a low/mid level player, and accordingly the results are better.
i have a lot of fun with a Mang0 styled Marth, but i feel its a waste to let those 3 years of Mew2King style Marth go away
It shouldn't go to waste at all. Take the parts of each that work towards making the best possible gameplan you can. Think about the goals and reasoning involved in the situations you encounter, and how the actions you see being used in them relate to that, rather than focusing on the actions themselves (and blindly imitating them). Look at the way different players will approach the same situation and consider what the different impacts of those approaches are, and why they've made the decisions they have. Think about what that might tell you about the possible differences in fundamental understanding/approach/conceptualisation to the situation or even to the game more generally.
Also, just because one player focuses on certain things and is good at them while being relatively less focused on and worse at others, it doesn't mean that you have to adopt their weaknesses when you copy their strengths.
No other marth does it though, and everyone knows how to get out of it or di out of it nowadays, and im not saying i wouldnt do that im just saying ahould i play with less grabs and more airiels kinda like how mang0 plays.
Nearly every mid-level or better Marth main does it, though of course they're not as consistent at it as Mew2King is. Even "creative" Marths like reaper or Mango do it and are competent at it, despite sometimes going for suboptimal things like up throw down air on FD instead. Note that even Mew2King doesn't chaingrab optimally, somtimes in really obvious/extreme ways like often going for up tilt techchases instead of pivot grabbing on slight DIs before up tilt starts tippering; he's just pretty well optimised and very consistent at what he does compared to other Marths.
People are better at getting out of it than they were. It's not a guaranteed 0 to death and hasn't been at any point (there's no overlap between the time when people were incompetent enough at DI to not be able to get out or survive and when people were competent enough at the chaingrab to be able to actually do it in the first place). It's still extremely good and worth doing. You can optimise it further than it already has been.
Recently i notice that im kinda playing a style that is slowly dying off, as all marths do nowaday are f smash without even spacing and dash dancing
That's outright wrong unless you're just talking about bad Marths, which have always existed and always will, and shouldn't inform you about the state of the meta.
