"In a non-work related situation, should I address strangers my own age 30s as вы or not?""
If you don't know a person well (it's a stranger) it doesn't matter what age the stranger is. Better to say "Вы".
For example, you are in your 30ies and I am younger (in my 20ies) but we don't know each other well and therefore you and I would say "Вы" to each other. When you get to know the person better it's ok to offer and ask "может, перейдём на ты?" Usually there is a positive answer
To people who are older - for example, you are 30 and you are talking to men or women who are 50 years old (even if you know them well) we always say "Вы" (to show that you respect them)