Seville

There are at least three full sightseeing days in Seville, more if you are taking it in a leisurely fashion.
You can see Cordoba as a day trip, but I think it is worth an overnight.
Jerez is interesting, especially if you like sherry.

Rather than spending all the time in Seville, I'd spend at least 2 nights in Cordoba and at least 3 nights in Granada. (Note that Granada is at altitude and is likely to be somewhat chillier). Seville, Cordoba and Granada are the Big Three of tourist destinations in Andalucia.

Other places enjoyed by many are Ronda and the small white villages scattered around the area southeast of Seville, coastal Malaga and nearby small villages, the Caminito del Rey hike north of Malaga, Jerez (sherry and horses) and historic Cadiz. There's much more, but I think those are the places most often mentioned.

If your major interests are the 3 main cities and the little white village in the interior, you might like to rent a car to cover the trip from Seville to Granada (or vice versa) with a stop or two along the way. Public transportation is a real challenge even if you only want to include Ronda and is not really practical on a short trip like this for reaching places like Arcos de la Frontera and tiny Grazalema and Zahara de la Sierra.

There are some sights in Andalucia for which you'll need or want to buy entry tickets in advance. The imperative one is the Alhambra in Granada. Those tickets can sell out weeks or even more than a month in advance. For other places like the Alcazar and the Cathedral in Seville, it's more a matter of avoiding a probably-very-long ticket-buying line.

My partner and I spent 11 nights in the Andalusia region and Madrid in Sep 2023, our first visit to these locations. Our trip report might aid your planning: https://community.ricksteves.com/travel-forum/trip-reports/trip-report-spain-aug-sep-seville-ronda-granada-cordoba-madrid

With 10 days, I'd spend about 5 in Sevilla, and then go by train to:

Cordoba..2 nights
Jerez..1-2 nights

Plus one other town/city.

Looking west and northwest from Sevilla is the region of Extremadura. While not generally an area people visit on their first, or even second or third trips, it is a very nice area. Trujillo, Cáceres, Guadalupe, and Mérida are very interesting cities as is Plasencia that is further north. Closer in to Sevilla is Zafra that is worth a few hours. There are many small villages and national parks in the area of the mentioned cities, but you’d need a rental car to make the best use of your time.

Where you visit should depend on what you want to see as well as how you intend to travel; rental car or public transportation.