Has anyone used the lockers? We were thinking about maybe going to Stein um Rhein on our 1st day and staying overnight there and keeping our suitcases in a locker. Would this be a good plan or should we just do this as a day trip and no overnight? Or, third option, staying overnight there and bringing the suitcases along with us. Also, has anyone stayed overnight there?
Store your luggage at the train terminal in Zurich so you can visit Stein um Rhein. No need to have an overnight stay. Make it a day trip then return in the evening.
https://www.sbb.ch/en/station-services/services/lockers.html
https://www.sbb.ch/content/internet/sbb/en/bahnhof-services/bahnhoefe/shopville-zuerich-hb.html
Zurich is discouraged as a place to spend the night. It's just not very interesting compared to all the other options in Switzerland.
An alternative to spend the night can be the city of Lucerne instead of Zurich then train from there to Stein um Rhein. Therefore, You wouldn't need lockers.