One thing with a smaller space is that it forces you to think very carefully about what you want to do. If you intend to build furniture, you do need some empty space to stand the growing carcase, and have some space left over to actually stand up in. That may limit the amount of machinery you can accommodate.
Working handtools only (or hand and hand-held power tools only) may not be everybody's first choice, but it doesn't half free up space. All you need is a bench, a pair of saw-horses, storage for tools (toolchest, cupboard, tool-wall) a rack for clamps and a cupboard for glues, screws and sundries. In a single garage, that would leave just about enough space for a project to stand, with a bit of breathing space around it. You do have to be ruthless with 'stuff' though, otherwise it very quickly dominates a small space.
Machinery might even be more bother than it would be worth in such a space. Even small machines need dust extraction, which is more space gone (and more expense and maintenance), plus infeed and outfeed space. Once you'd got a bandsaw, planer-thicknesser and SCMS in, with dust extraction, there'd be no room left to stand a job in, unless you confine yourself to small work like jewellery boxes.
I know it's entirely a matter of personal choice, and I'm certainly not suggesting that machine use in a single garage is impossible, but free space is something very few people consider when planning a workshop; when you don't have any, you certainly learn it's value!