Third -- There is all this talk about sharing folders over the internet and remote management of SBS Essentials -- but it looks like actually running AC remotely would still require RDP to a client machine in the office that I would access remotely as I do now. Looks like the remote machine (at the beach, say) wouldn't really be a "client" of the SBS Essentials -- that would be too slow. Is that true? It is so confusing, and I can't find any documentation anywhere that just answers basic questions -- all the Microsoft stuff looks like sales brochures, and the various tips and helping hands are scattered everywhere in blogs.
Yes, you'd just be using RDP to a client machine. Just as we recommend with any main computer; you should not be working directly on it. You should be able to RDP to any PC on the LAN without having to open ports for them. The only one you need is 443 which isn't blocked like 3389 (Remote Desktop Default) is in a lot of places.
You can direct access files as show in the image below. Possibly run Word/Excel/PowerPoint over a web browser if necessary (Office 365):