I haven't tried these shoes but I have walked all or most of the route you are planning 4 times. I offer the following with the hope it may be helpful in your decision making.
Most of the Leon - SDC segment of the CF is on agricultural roads, some are paved, but most are gravel surfaces. Running shoes like those you are considering should do fine on these surfaces. There are several sections of relatively flat dirt tracks that can be muddy when wet, but again, runners should work . I have found that sole cushioning can become a consideration on gravel surfaces when rocks are bigger than 2-3 cm in size. The tech specs for the shoes you are considering shown on the REI website (
https://www.rei.com/product/216764/saucony-kinvara-14-road-running-shoes-womens) indicate they have "moderate cushioning" (whatever that means). The heel stack is 31mm and the toe stack is 27 mm, which is reasonably thick cushioning. I have had no problems on rocky paths with Altra Olympus 5 which 33mm of cushioning, but the materials may be different.
In a few places, comprising probably less than 5% of the distance you will walk, are more challenging. The first is the last section of the descent from Crux de Ferro to Acebo, which is very steep and rocky. If your shoes lack traction here, especially if the rocks are wet, you will have problems. Hiking poles are very useful in sections like this but traction is probably the most important consideration on this type of trail. You can by-pass the worst parts of the this ~ 4-5 kms by taking the road, but that has its own dangers and requires watching carefully for vehicular traffic.
The next possible problematic section is the climb to O'Cebrerio where a rough, rocky climb can be complicated by mud and horse manure. Again traction is the issue if the trail is wet. The horse manure is a problem regardless of the weather, but it is easier to avoid if you're paying attention.
There is also a moderately steep dirt path uphill section leaving Sarria but that can be slippery if it's wet.
To my memory those are the only sections where running shoes built for paved hard surfaces might be a problem. In these sections the lack of traction could be dangerous, so if you go with these shoes you will need to be sure of foot placement in wet conditions. As mentioned above, hiking poles will help.
Hope this helps.
Buen Camino!