Lovely home and the roses look great. To make suggestions we need your location.

6B. I’ll add it to my post!

The color and flower combinations would be quite lovely.

Would be good to know how much distance between the roses( when at mature width) and the porch wall as well as height off the ground , because the Annabelle’s will want 5” in all directions, I believe. Yes you can prune but not sure you want to be doing that “ defensively “ to keep from crowding the porch and the other shrubs.
So akso coukd be re- thinking whether everything has to be in rows, or have , say, a roomier spot or 2 for hydrangea to do its thing.

I line Walker’s Low- it’s especially beautiful with deep pink or red roses. It does creat a big mass of wiry stems that need to be cut down each year sometime before new growth.

The thing about these plants is they’re all deciduous so will be bare stems all winter— sure you’ll likely be cozy inside during those months, but is that a problem for front of house design? Or would you like s few evergreens.

Annabelle hydrangeas will not do very well in full sun, which I assume you have since the roses are growing there. Perhaps look at a dwarf version of panicle hydrangea instead, which are far more sun tolerant and even need sun to flower well.

Also "alternating" different plants rarely produces a desirable look. Too regimented and contrived.

I'd also go with a dwarf or compact form of nepeta. Walker's Low gets huge!!

I agree that Annabelle hydrangeas are probably not the best choice. Maybe consider Rose Creek abelia instead. And I am a huge fan of catmint. Very reliable, pretty purple flowers spring through fall, and deer do NOT like it.

Running nepeta along the entire frontage is an awful lot of nepeta. In your "before" photo, it looks like two perennials were used for edging - one in front and a second along the rounded "ear". Perhaps you could have nepeta in front and calamint/daylilies/dianthus/etc along the rounded ear.

Which nepeta to use depends upon your aesthetic. Some people like to see visible mulch between plants while others want the plants to grow together and cover the mulch. If you want your nepeta to grow into a solid mass use Walker's Low. If you want rounded mounds of nepeta with mulch visible between them use Junior Walker.

I would want to establish why 'everything except the roses' died. Nepeta likes the same conditions as Lavender and your Lavender did not survive ....

My guess, and this is really just a guess, is that the location is south-eastern Pennsylvania, and the issue with the other plants is they don't like a heavy soil with a pH in the low 5's.