If you are staying only a week I suggest you concentrate on a portion of the island (most people, including Sardinians, will agree the northern half is better)..
The place is big and it takes time to travel around the island as roads tend to be curvy and slow. There are some freeways but not likely to serve a purpose to a visiting traveler since they are in the interior and not on the coast.
Not many Americans visit Sardinia probably because it’s inconvenient to include it with a trip to Italy due to its geographic location. Also it doesn’t have the wealth of historic places to visit like the rest of Italy. Sardinia is famous for its natural beauty, particularly the sea (and under the sea if you are a scuba diver).
If you use the “search” function above you might see several past posts with replies from those who have been there. I’m one of the few who has visited multiple times, albeit I haven’t been there in a few years. Try to search and in the meantime this is a post from the not too distant past, but there are many more. Just enter “Sardinia” in the search box and numerous will come up.
https://community.ricksteves.com/travel-forum/italy/sardinia-a4b6bf34-12f0-4f41-aa46-cc7c08ab1f7f