If you are in the bay area, I would avoid single speeds, I wouldn't recommend a vintage bike as a commuter because it might not be the most reliable bike. If you are willing to learn about doing mechanical stuff yourself, and investing in some tools, it can be really fun.
That said, fuji gang.
I'm not a huge fan of those build it up direct sale entry level bike stores, you really get what you pay for, they often cheap out on lesser thought of components that later on will cost you. Cheap bearings, tires, rims, bottom brackets.
Try and find a roadie, or gravel bike that fits you new or used. Get fitted or use a sizing chart, nothing worse than buying the wrong size.
I ride a trainer in the witner, it keeps me going, i ride on zwift, its "fun", its better than not riding, and I am usually pretty fresh when spring riding comes back.