Thank you very much for playing the game!!! Really appreciate the feedback :D
I really did mess up with the audio haha. Apparently there is this new thing with Godot web exports, where they use samples instead of audio streams. This became an issue for me because that meant I couldn't change the pitch of sounds :(
So I changed the setting to use streams instead of samples. By doing that, all the audio is now being mixed in one thread, hence the lag.
I will try to find a fix for this as soon as the voting period ends :D
Thank you again for the kind words :D