On our Trek Pack, we include a link to the Trek View website – it’s a great way for people to discover the project, understand our ethics, and usually what they’re most interested in, to be informed of when imagery of the location they were captured goes online via our Spotter a Trekker form.
We used to print cards with information on, but they were needed so infrequently that we stopped bothering (https://www.trekview.org/blog/2019/diy-google-street-view-part-3-preparing-to-shoot/).
Wearing a high-viz vest will make you look more professional, and people will probably be more likely to leave you alone, but I don’t bother personally.
Some people will often want to stop and ask questions. My advice, stop and chat. Stop the camera for a few minutes and explain what you’re doing.
The biggest concerns around privacy, and quite rightly so. Here at Trek View we have a policy of immediate removal of images if there is a complaint. No questions asked. If someone asks us en route to do this, we mark the time, and make sure these images are deleted from the camera before uploading. Despite taking photos being legal in public places (at least here in UK), I just don’t think in such cases it’s moral to take the legal high ground (nor sensible).
Parents with children are usually most concerned. Again, quite rightly so. Therefore we advise trekkers to avoid parks where children congregate, or perform captures during school hours (when schools were open).
At the end of the day be sensible, be approachable, be polite. 99% of the time this should be enough. Occasionally you might get someone who digs their heels in, where nothing you could have said or done would have helped.