@Cernel No, you need the territory attachments listed before the unit attachments as that is where you define which territories have territory effects.
It will always use the territory instead of the territory effect in the rare case you'd have a name conflict.
You can use restricted or allowed with territory effects just like territory names.
Long term, many places where you can specify territory names, I'd like to allow territory effects so I want to avoid duplicating lots of unit options.
@Frostion The tooltips will actually show a list of the territories as the engine maps the territory effect to all the territories that have it when the map is parsed. It should work for sea unit placement as well (you could have say a "coast" territory effect which is required for certain sea units). The territory effects only influence the territory that the unit is being placed in (land or sea) so having some territory effect where the land factory is has no influence on what sea units can be placed. But you could have land territory effects that limit what infrastructure can be placed so for example you could limit "naval base" unit can't be placed where there is a "mountain" territory effect.