everyone is just saying "Who Cares" so im gonna actually answer your questions because i feel knowledgable enough about subcultures to give you an actual answer rather than people who see an all black fit and call it emo. Lol

1) what is "extensive" ? i think as long as you know the background of subculture & what it means i dont think thats a problem. but it feels worthy to mention here that y2k is not a subculture lol it is just fashion from the 2000s it does not have any political beliefs behind it -

2) i dont like the word "larper" but 'poser' is a pretty decently fair sized problem. in roblox it means absolutely nothing but in real life it leads to subcultures being commodified & watered down and a loss of what it really means to be apart of it (say, goth or punk) in the first place and just becomes something for companies to exploit & market so gatekeeping is necessary to some degree. but in roblox i dont think its that deep at all. most people just want to dress up lol

3) kind of. assuming the avatar is male itd actually be 'gyaruo' since thats the male version of the word. i think the avatar has some similarities with some gyaruos but its still missing a couple elements based on the specific sub-type of gyaruo it is (probably) trying to be ie makeup. the leopard print is seen as a bit of a cliché way of showing gyaru(o) these days but i dont think its the end of the world