That screw-top thread is the normal one: the plug cap on the spark wire has a little socket that ratchets onto it. If the ratchet isn't working, it is broken. New plug caps are about $5 each at most bikes shops.
Use the B8EA or B8ES with that engine. The "R" designation in the part number(s) you mention are resistor-type plugs.
Here's the inside skinny:
Honda made those bikes with plug caps of 7500 ohms resistance, intended to use on B8ES (or B8EA) sparkplugs from NGK. As the years and miles went on, the plug caps can slowly degrade toward 8500 ohms. Once they reach that value, the spark will try to escape out the boots to places like the engine, or your leg, in the rain (don't ask...). At that point, you need to replace the plug caps. They usually last about 8 years or 15,000 miles or so, which ever arrives first.
Today, you can usually only get 5000 ohm plug caps or 10,000 ohm caps. So, your mechanic probably assumed you had the 5000 ohm type (if new) so he recommended you also use resistor sparkplugs (they are about 2000 ohms) so as to closely approach the OEM Honda design. That's not a terrible idea, except the plugs are hard often to find. So, if you use the 5000 ohm (new) caps or good old caps (7500-8500 ohms, no more) you can still use the D8EA (or D8ES) plugs just fine.
You can test the plug caps by unscrewing them from their coil wires. There is a little screw on the wire end. Touch that screw with one probe of an ohmmeter, and the little socket inside with the other. It will tell you what the resistance is: then check it against the above numbers.
