The problem is that my actual rendered video itself was soft/blurry looking – unlike the original imported clips – looking just as it did in Preview (Best), which I had been using. I just did switch to Preview (Auto) on your suggestion and will try it that way by re-importing several clips and seeing if they’re sharper in the final rendered product.
Perhaps my Render Settings are not optimal either, since I’ve seen several different variations on what is considered “Best”.
I may need advice on the definitive best render settings as well.
Thanks for your reply, John!