I'd say that the FWDs in EPR are fairly accurate. Probably more so than GT5P, though not quite as easy to drive as the steering response in EPR is a bit muddy so you need to be very deliberate with your actions, and I personally find the brakes hard to modulate in EPR so I can't drive any car as smoothly as I can in GT5P.
Yes - there is lift-off oversteer. This is especially noticeable when you're trying to set hot laps at tracks such as the 'Ring, where trail braking and lift-off oversteer can get you into all sorts of trouble if you aren't careful.
I'd say that understeer is implemented fairly well. I had my reservations at first because I thought that the inside front wheel was a little too ready to spin when powering out of corners, though it was pointed out to me that it wasn't beyond reason at the sort of speeds you can experience in a game, which aren't often replicated in real life.
The different cars certainly handle very differently - I've driven the DC2 Integra Type R and EK9 Civic Type R a fair bit recently and it's quite easy to tell the differences, with the Integra feeling a little softer and rolling into oversteer more easily, the Civic stiffer and cornering better but a little harder to turn in on the brakes as a result - and these differences apply to any of the cars. In this respect it's better than GT4 for sure, and I'd even be tempted to say better than GT5, if not quite as fun owing to the extra difficulty, and the extra patience you need as mashing the throttle just doesn't work.
Overall, I'd say the game is equally impressive with FWDs as it is with RWDs and AWDs.