If the toaster had a metal shell which could come in contact with a live conductor, it would be required to be earthed, as a Class I appliance. An RCD would absolutely guarantee a trip should such a fault occur, but would not be required for protection. A Class II (double insulated, non-earthed) appliance must be designed in such a way that a fault of that type cannot realistically occur. An RCD is not required for either case in normal installations. You are right, however, that an RCD would trip should you have a live, non-earthed metal case.
GFCIs work exactly the same way as RCDs, yes. They have a coil (current transformer) internally through which the line and neutral conductors are passed. Should there be a difference in current between them (current flowing back via another path, ie. either conductor contacting an earth path), the CT will register it (if the current is equal, it's cancelled out, and the CT registers no current). Once that imbalance reaches a sufficient level, the device operates. These devices are, except for minor differences in current level and reaction time, the same all around the world. No earth contact is required at the RCD itself, nor any device it protects.
I would suggest not feeding your entire bench from the RCD strip, and merely feeding devices you're working on and test circuits from one. Anything which is well made and intact does not require the protection, and having your entire bench go dark is pretty annoying.