Hydrangea arborescens is native to your area so consider Annabelle and its cousins Incrediball, Spirit, etc. But make sure it does not get too much sun (8 hrs may be too much). Paniculatas can handle more sun than arborescens so consider them too. Have you contacted local sources? See the Master Gardeners Of Northern Virginia's website mgnv.org

They mention https://mgnv.org/plants/shrubs/whydrangea/ for part shade

I wouldn't use H. arborescens or H. macrophylla in a settng with 8 hours of sun since both do best with morning only sun or dappled sun. I'd use some variety of H. paniculata which is the most sun tolerant of the hydrangeas. I am in a much cooler setting than you, but mine do fine in all day sun. I don't know how they would do for you in VA, but none of the other hydrangeas will be happy with 8 hours of sun in your zone.

As far as combining boxwoods with hydrangeas, I'd first be sure that you and other family members are fine with the scent of boxwood foliage since you are looking at using them around a deck. Some folks are fine with the scent, but some folks find it extremely rank and unappealing, so wouldn't want it where they will be spending extensive time. If you are fine with it, I'd visit the blog of Deborah Silver, a Detroit area designer who uses both boxwood (and other evergreens) along with hydrangeas. Just type boxwood or hydrangea into the blog's search box and you will get a number of posts that include plantings that use one or both. Most of the gardens she plants are fairly formal, and often she plants rows or hedges of Hydrangeas, often combined with evergreens such as boxwood, yews, or arborvitae. Her most often used H. paniculatas are Limelight and Little Lime, but there are a wide range of varieties that vary in plant height and width as well as in branch stiffness (stiffer branches hold the flower heads more upright) and the shape, size, and density of the flower heads. My favorite is Quickfire, which is about 6' in all directions and has stiff branches that hold the flowers well upright. The flower heads are lacy looking and rounded and bloom for a long time, changing from white through pink to a rich cerise over the course of 4 months. In warmer areas I don't think the flowers last as long.

Here are photos of a couple of mine which are planted in informal mixed borders.

Quickfire early July.

QF mid-August

QF color Labor Day until frost - doesn't seem to change or fade for several weeks

PinkyWinky color late August; it starts pure white in early August.

PW late September

PW mid-October

If you do a search here on the GW hydrangea forum (type paniculata into the search box and then click on the option that pops up to search in Hydrangeas) a good number of discussions will pop up about the various types Hydrangea paniculata, many of which include photos.

Your Quickfire looks very lovely as well as that lovely Pinky Winkey. I looked up with the local nursery; none is available in my areaSo my husband got me limelight hydrangeas, picking up more on Friday as well as phantom hydrangea trees tow on each corner of the deck. I was thinking of finding another evergreen to plant along with the hydrangeas so far no other comes to mind. So far I am due to plant this weekend, and I am getting nervous as to which other plants to include in my flower bed.

Since you have Limelights, be aware that they can get large, and IME pruning doesn't reduce the size by much since they regrow quickly. Limelight can get to 6'-8' in height and width, so be sure to plant it at least 4' away from the deck.

I am unclear how you are planning to use the evergreens; in front of the hydrangeas or in the same row as the hydrangeas or . . . ? I think that the Limelights are large enough that you don't want your evergreens to be taller than the hydrangeas. If you want a front row of evergreens and if evergreen azaleas and rhododendrons do well in your area, you can find one that stays around 3'-4' to use. That might not be an option that you will be able to find this fall already in nurseries since around me they tend to carry larger-growing varieties, but you could order them now for next spring and plant them next spring. Have you checked out boxwood for how you like the scent? I don't find it appealing, but some folks do. You could ask on the GW conifer forum for slower growing or low-growing conifers to use in a row in front of the Hydrangeas. I know that there are dwarf and semi-dwarf Thuja (AKA arborvitae) cultivars (if you don't have deer which love to eat Thuja IME), but I imagine that there are probably other possible conifer options. I don't know if there are any evergreen herbaceous or semi-woody plants that would work. Lavender or rosemary wouldn't work since they like conditions much drier than the hydrangeas, but you could check in the Perennials forum to see if there are any mid-sized or large perennials that stay evergreen in your area. There aren't any in my area, but I am a whole lot colder than you are. The shrub forum may also be of help in suggesting other evergreen shrubs that will stay small enough for a row fronting your hydrangeas.

If you are planning to use them in a different way, let me know and I may have other suggestions.