If you have deer problems then I'll will advise you a plicata.
The plicata cultivar with the most dense habit is 'Atrovirens', all it's sidebranches are going upwards while the sidebranches of the 'Gelderland' are going sidewards.

The 'Gelderland' is a Dutch selection and found as a branch mutation on a 'Excelsa' by Leen Konijn and named after the province it was found in.

Thanks. How well will Atrovirens do in bright shade - i.e., a few hours of morning sun and a bit in late afternoon? One reason for considering Wintergreen is that is supposed to be the most shade tolerant, staying dense all the way to the ground. I've read that it is also the narrowest of the Thujas.

'Wintergreen' aka 'Hetz Wintergreen' does have a good pyramidal shape, it arose as a seedling of 'Pyramidalis' but by far it isn't the narrowst of all Thuja occ. cultivars.
Some more narrow one's are 'Degroot's Spire' and 'Green Pillar'.

Thuja plicata 'Atrovirens' can grow in bright shade, no problem.
I prefer a plicata over an occidentalis because of it's rooting system, plicata roots will always go straight down and find the water they need also in dryer periods.
Occidentalis roots won't do that and grow more on the surface which could be the cause in dry summers that they won't find all the water they need so they loose colour, start to drop their needles and will produce (a lot of) seeds.

B.t.w. I never saw a Thuja plicata 'Atrovirens' with seeds,
maybe it's sterile which is also a very good thing for the perfect dense hedge conifer.

Thuja plicata 'Atrovirens'
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Completely different clones are sold as 'Atrovirens' over here. The original distinguishing feature was that it was deeper green that typical, otherwise the same. Old Latin cultivar names like this may go back so far that there have been numerous independent introductions made under the same name, as well as the usual mixing up that goes on in nurseries.

I once heard the complaint from a retailer here that a grower with a large block of a western redcedar cultivar was telling prospective buyers they were whichever generally similar cultivar they were looking for. If they asked about 'Atrovirens', that's what they were. If they were wanting 'Green Sprot', that's what he had and so on.

Just looking at these "hedging cedars" (name used in Lower Mainland of BC) in local retail outlets I cans see that variety names have become quite mixed. You will therefore have to study any stock being considered carefully and in person to see if it looks like it is going to fit the bill. Keep in mind that considerable broadening may occur with age, and that any western redcedar selections not of a dwarfed nature are likely to become towering with age.

Partial shade is no problem with any kind of arborvitae, but heavy shade makes them see-through thin. Here in its native area western redcedar is, along with western hemlock a climax species that often comes up beneath taller, long-established specimens of other species and gradually replaces them - as long as fire or other stand-reducing disturbance remains absent.

Thanks, everyone. I'll go check out some of the plicatas in the local nurseries around here this weekend. Narrow and shade and deer tolerant are high on my list!