I think the oil recommendation difference might be based on the fact that Europe doesn’t use leaded fuel. Lead is really nice for internals of two strokes and still universally used in the US with two strokes.
Also great for cancer. But I digress.
The most important thing is to stick with what your engine builder recommends. That way when they give you advise, you’re on the same page. Different oil ratios affect jetting.
Circling back to plugs: this is a good read.