Geoff, the extra photo confirms the presence of an emarginated 6th primary which is diagnostic of Greenish Warbler and is never shown by Arctic.
An emargination is essentially the tapering on the outer web of a primary feather (the equivilent on the inner web is called a notch). On your Greenish Warbler photo these can be seen on five primaries and as the first primary is very short, these are the 2nd to 6th primaries.
BTW, I think your photos of an Amur are in fact a juvenile (northern type) Peregrine (note the very dark underwing and upperparts, extensively streaked brown - not black - underparts and overall impressive of a heavy, rather bulky bird).