Yes, absolutely do go to Uni open days. We couldn’t go to any due to Covid, but did still go and had a look around outside when we were allowed to, just to get a feel for the uni’s/campus/city and general areas for each. Once you have identified which uni’s are offering the courses you are most interested in, it’s definitely worth going and have a proper look around and see what they offer, ask any questions you may have, and just see how it feels to you. Can you imagine yourself living in this place, is the climate suited to you, is the cost of living there manageable etc. Somewhere which may currently be top of your list, may turn out to not be to your liking after visiting, so it’s important to visit if you can.
A lot of people don’t drink or don’t drink much. My daughter has just started her 2nd year at Uni, does like a glass of wine or cider, and loves clubbing. She will have a drink in the JCR in her college before going out, but then sticks to water whilst out. They even have some clubs and activities for those who don’t drink, so I’m sure you will not be alone. You can still join in with other people and events and enjoy yourself with soft drinks and that’s fine. People will get to know and like you as you are, and you’ll soon find good new friends who like you as a person.
Good luck with A levels and with your Uni choices.