16-day Itinerary Advice

I think you will feel very short on time in Barcelona and Sevilla. If it were me, I'd drop Madrid, stay a night in Toledo, then head to Sevilla. You will still be short on time, but I think it'd be better.

Thanks Jules, we’ve been to Barcelona and seen many of the major sights, so we’re really focused on seeing Madrid, Seville, Granada and the Andalucia region for the first time.

With the places you have chosen to visit and traveling by train, you won’t find many castles. Many are in out of the way locations not near train or bus stations. If you had a rental car for the entire trip and didn’t mind small towns and villages I’d recommend a number of castles worth going to. There are even some you can stay in, e.g., the Paradors at Sigüenza and Alarcón. Since Córdoba isn’t on your list, you’ll miss out on the Mezquita; formerly a mosque.

I'd fly from Barcelona to Granada. Then drive via Ronda, etc. to Seville, then take the train to Madrid.
Personally, I wouldn't bother with bullfighting which is evil or flamenco which is boring.

Sevilla is gorgeous with so much to do. You wouldn't see much of it with one day. Could you fly into Madrid or Sevilla and skip Barcelona?

My wife and I (mid-60s) spent 11 nights in Spain in Madrid and Andalucia in Sep 2023, and share most of your interests. Our trip report might be useful reference: https://community.ricksteves.com/travel-forum/trip-reports/trip-report-spain-aug-sep-seville-ronda-granada-cordoba-madrid

How about this:
Barcelona (2)
Cordoba (1)
Granada (3)
Ronda with Car (3)
Sevilla (4)
Madrid with day trip to Toledo (3)
Fly home from Madrid