I am planning on speedrunning this game, which category is recommended to start with? Any% version 1.4.2 seems to be the most competitive.

Or maybe I should start with some ILs?

Ok since nobody answered me (and because I am very impatient) I'm just gonna start running the categories that appeal to me the most.

1.4 online is the best to run (at least for me) 1.5 is laggy and just unnecessary to run good luck on running! (please dont murder my runs into oblivion )

Alright thanks, will try to get WR on that one soon then. Vexxter's run seems to die multiple times so it could definitely be improved.

of course but i cant do it

The performance is kinda random, but most of the time Windows is better than HTML5.
Also Windows version actually saves files. The Web version also saves the game data but in a virtua place somewhere in the browser files and the only way to see the files is with the developer options.