As I said above, you shouldn't see any difference when the game is open. However, when the game is closed they should earn tech points roughly four times faster at 2X than on half speed.

They won't gain any more points per try, they'll just get more tries in the time. The level of points earned depends on whether the scientist is untrained, a trainee, adept, or master, and also on the level of Science tech you're at.