5 is good. I think more is meant to be even better, but 5 is "enough". Get up to 5 then think about whether you can manage more, don't think there's no point bothering with 5 because 10 would be even better IYSWIM?
Mixed veg would count as 1, it doesn't have to be all the same. So a portion of fruit salad counts as 1, and so would your mixed veg bag.
I don't think there's any rules in terms of the health benefits, but you're probably getting quite a lit of sugar if you have 5 portions of fruit a day, so you have to consider how that balances up with the rest of your diet.
HTH!