You've got the right idea, terraced houses are better mapped as individual units. The tags you're looking for are building=house and house=terraced. There's also no need to put an outline around the whole block of houses, having them connected and all tagged as terraced is enough. I'll do a quick demo edit with the ones you've done already, but feel free to reach out if you have any more questions. Thanks for contributing to OSM and welcome to mapping Cambridge!