You only need to achieve their minimum so AAA is perfect. Getting higher grades does not get you any extra points against candidates who only get the minimum - it’s just a check in the box for meeting requirements and that’s all (maybe exceptions for Cambridge). Once you’re over the minimum threshold you’re all good, but work experience is also a minimum requirement + what you discuss in forms and interviews etc so it is probably even more important. I’m not sure about widening participation for international students sorry, but you can always email or call up the unis to ask.