I have the same issue. The crazy part is on my laptop which is a 2060 mobile it runs amazing. No issues at all. It does have an external monitor though which I play on. When I play on my tower. With a much stronger processor and graphics card. The game is unplayable. Same internet connection, better specs. I can’t figure it out. I haven’t tried running dual monitors yet. But still I don’t see how that would make a difference. Also single player and challenges are fine for mut. It’s only head to head of any kind when it happens.