The “turbo” name typically has meant that the engine uses a “turbo plug AND has more than 3 ports.
The OS "TZ" engines have turbo plugs and 5 ports.
A turbo plug is different than a regular plug in that it has a tapered end that fits snugly with the button, removing the need for (as you said) a washer. Turbo plugs result in a cleaner combustion chamber and thus can help produce more power. Also, turbo plugs can’t be put in a non-turbo engine, and visa versa. Although for non-turbo engines you can just replace the button (the part of the engine the plug screws into) with a turbo version.
The “5 port” sleeve in the TZ engines is a much bigger performance gain than the turbo plug. Typically the more ports, the better the flow of air/fuel can be managed within the engine, and thus more power.
Note that if you race, then there may be rules about whether or not turbo plugs are allowed or if your engine can have more than 3 ports. Check the rules before you buy.
Hope that helps.