Circuits in the sim are generally quite difficult. The tendency to overcorrect combined with the poor visuals make it a difficult maneuver. I recommend to fly the profile as perfectly as you can, with a few glances out now and then, to verify that you are indeed still visual with the field. (Be very accurate with tracking+timings) When turning base, stick to the profile you've been taught, 200-300 V/S works for me, and adjust the bank angle selector so you align the trend vector with finals. Don't forget to readjust your V/S (7-800) once on the PAPIs and disconnect.
I think the reason behind all this is that the 737(-800 at least) is unforgiving if you're not on profile compared to smaller aircraft. You need to be quite accurate. But, hell. Once on line, if you can fly a visual primarily looking out then there's nothing stopping you.