I don't think the pro mode is that much more realistic than the standard, it's just massive understeer at every single corner no matter how fast you enter, or what car you are driving.
Having said that, I still use pro mode but after 5/6 hours on the game, i'm bored of it
Online play is quite smooth but it's just full of NFS players (in the lower ranked cars), once you get the faster and harder to controll vehicles, the racing is a bit better but too many a time I find myself being rammed out of a corner by somenoe who doesn't use his brake pedal...