I don't want to encourage speeding but they don't know where you are so nothing less than 70mph should be an issue with a black box. It's more to do with harsh acceleration and cornering I believe.
Not very helpful probably, but I wouldn't definitely say get a car with a smaller engine. My 1L Yaris is far nippier than a number of 1.4 and 1.6s I've driven anyway. :shrug:
Don't think age makes a lot of difference until at least 25+ but could be wrong.