There's already some signs of triangles in osu!lazer. Not the same effects as before (main menu background and menu transitions) but they're there (osu!cookie background, button backgrounds and hitbursts). I don't know if the previous effects are gonna be back. And I'm not one of the developers, no way I can fix lag! osu!lazer is supposed to run smoother than our current build if you wanna know so I think this will fix your lag problem.