Multi-location business helps or hurts SEO?

I am prepping for marketing in the new year and something I'm seeing a lot is related to registering my business in multiple cities, because we have locations in 3 cities across the U.S. Currently, we only have one physical/public setting office, and that is the only place our website and GBP targets. However, I'm not sure how adding the other 2 cities will affect my SEO? Hoping this will help get more eyes on my website due to having more local traffic options for each city we're located in, but not sure if it will have a reverse effect of decreasing traffic due to spreading ourselves too thin (we wouldn't have much content specifically targeted to each city). Also, I know you can set a non-specific address in GBP but does anyone have experience with that, if this sounds like it will do more harm than good, etc.? Any advice helps, thanks in advance!