You must be aware that new tire temperature modelation, it takes a little to get it to proper temperature, until then the cars are all over the place, specially on racing tires. The harder they are, also take more time to get to temperature. After having them warmed up, most of the cars behave as they should. Pre 1.31 they just look like they were slot cars, with the front going wherever you point it.
Yes, if you brake and turn at the same time, it will understeer. If you have a huge rake angle (which worked great before 1.31), on corner entry all the weight will be in the front, it will understeer.