go to your local parts house (AutoZone, Advance Auto, NAPA, etc) and ask for regular NGK plugs to fit a 2001 protege with 1.6 engine. the 1.6 plugs for the US are the stock 2.0 plugs that come in the JDM FS-ZE. they are extended reach, and work fantastic in the US protege 2.0 engine.
Yes, ZFR5's are the long reach and those combined with the 1.8 coils do make a noticeably smoother idle. They also aren't located on top of the hot ass engine. But you'll need to trim 2 spark plug boots to fit around the oem coil mounts or get a 2000-2002 626 valve cover that doesn't have those coil mounts. Make sure it has cam sensor hole on front like ours if you do, only those yr models are the ones to get.i think those are the zfr5e, im not a hundred percent sure though.
the 1.8 coils are larger, the idea is that they will produce a better spark at higher rpms than the smaller stock coils.