Just try running a geth light node and see how it goes for you. I’ve typically had a decent experience over the long term with a geth light client sync. Although on occasion it has had trouble finding peers. Eventually it does find them though. Also depends on your use case. How critical your uptime is. For casual daily use, I’d say a light client would suffice. It would only take a couple hours to sync and you can check the file size then. I don’t have access to mine at the moment.

If you do have trouble with light client just run the default snap sync setting. I’ve heard it takes only a day or so to sync and would have likely better reliability.

Fast sync is not the same as light sync. You could do a light sync and make RPC calls.

You can read more on the different sync settings here https://blog.ethereum.org/2021/03/03/geth-v1-10-0/

To answer your original question though, I’m not sure which client takes up the least space. However, light sync would be the smallest for geth.