[FairyKing]

If we go by the literal definition of tokusatsu, "live-action filming with heavy use of special effects," that would also include a huge amount of western fantasy, scifi and superhero movies and shows.

I think my unpopular opinion about what is and isn't toku is that there's no clear dividing line. There's some things that clearly are and some things that clearly aren't, but there's a whole bunch of stuff that's in a gray area. I expect most of us have a clear idea of what shows we're thinking of when we say "toku," but any set of rigid rules to define what is or isn't toku will end up either including things that we wouldn't consider toku, or excluding things that we would.
Maybe instead of asking "is this toku or not?" the real question is "how much is this toku?"