I wouldn't pay any attention to Premiership reserves personally, although on the basis that Cambridge were terrible last season I'd keep an open(ish) mind with Heath.
Seen a few of the Everton Vs Liverpool reserve games and they can get rather heated at times. Not sure if they still do now mind but they used to play up at the Deeva Stadium and would draw a few thousand.
Strong teams usually from both sides as well so it was quite entertaining usually. That porky kid that plays for United now looked half decent even back then.
You never can tell though some clubs pish about and treat as a game in the park about while others take it far more seriously and give it 100%.