Always good to ask questions about security.
I'm looking at options for security to make sure no one will have
access to my passwords/ bank account or other sensitive information.
I do use a VPN and keep it on during travel, but the improvement in security is less than it used to be, fortunately for a good reason: Today, more websites use secured, encrypted connections and any reputable bank website will certainly be secured, so your web traffic can’t easily be intercepted.
I also think VPNs are best for those with some experience with computer networks. For example, VPNs are sometimes used for bad purposes so many websites are suspicious of traffic coming from VPNs and some will even block them, so that it looks to you like the Internet is down. What do you do about that? A tech-savvy person might know that a workaround is to switch to another exit node to change the IP address that your connection seems to be coming from, but a non-technical person might not know the real cause of the problem and get frustrated while trying to make online arrangements during a trip.
A bigger risk is someone or maybe even a room security camera watching you enter your username and password while you stand in line, or sit in a waiting room at a station. A VPN can’t prevent that, but what can is a secure, trusted password manager, like the Passwords app that comes with an iPhone (I’m not familiar with Android phones). It can fill in passwords instantly without error, with the great advantage that no one can see which keys you pressed because you didn’t have to type your password.
Another more likely risk is that if you’re not careful to make sure you’re on the right website, you might enter your username and password on a fake website that just collects them for criminals. People have entered sensitive personal info into airline reservation websites and passport renewal websites that they did not realize were fake, so all that info went into the wrong hands, plus they never get their tickets or passport because the real websites never got their information. Just be mindful about checking the spelling of web addresses you type, or use a bookmark of the known correct web address.
On the street, be mindful of surroundings and keep a good grip on your phone to guard against grab-and-run phone thefts (often reported in some areas). Also set your phone to a short period before it locks. It’s a pain to unlock often, but if it’s stolen while unlocked then they could REALLY dig into all your personal info that isn’t further secured on your phone. For example, if a thief on a motorcycle grabs your phone and speeds away, would they be able to tap a bank app on your unlocked phone and gain complete control over all your finances? Or will your bank app require sign-in and stop them?
I’m not sure how Google Pay works, but hopefully it works like Apple Pay: When you use Apple Pay, the store sees a virtual card number that is not your actual credit card number which is never exposed. This can greatly reduce the chance of your credit card number being stolen so now I always try to use Apple Pay first; if they don’t take it then I use my actual credit card.
Side note: Being aware of the percentage cut that credit card companies take, in small non-chain/family businesses I will often try to pay cash so that they can keep all the money for themselves. By the way, for getting cash at ATMs, I use a debit card for a secondary account with only a modest amount of money in it in case someone drains it. Also, stick to ATMs that are clearly run by an actual bank, to try to avoid fake street ATMs that just harvest data.