Tags can be very generalized about sizing - to the point where they may be meaningless. And location can have a big impact on how big the shrubs can get. One of the major nursery suppliers for this area (actually one of the largest in the country) has the mature size of PJM Compacta at 4' by 4'.

I would look at tagged sizes as guidelines at most.

Yes I agree. I just don't know whether to put the Nova Zembla in front or the PJM compacta in front. According to the tag the PJM compacta only grows to .6 metres high compared to the NZ that says 1.2 metres tall. I don't want one to block the view of the other, (at maturity) yet the one labelled PJM compacta is already close to one metre tall and the NZ only about .4 metre.

'Nova Zembla' gets a lot bigger than that. And in general large leaved things should be at the front of plantings, rather than the back. Probably to resolve this you need to put the 'P.J.M' derivative to the side of the much bolder plant, instead of behind or in front.

Nobody can comment on the identification of the one without information about how it looks.

"And in general large leaved things should be at the front of plantings, rather than the back."

I wouldn't worry about this at all - it's not a concept you are going to find emphasized in any landscape design text :-) What you want to create is just the effect of some textural contrast so the two in proximity - the PJM staggered slight in front and to the side - should achieve that effect by virtue of the different foliage sizes (and shapes).