order of cities to visit and comments please

The order is fine. My concern is the pacing.

That's really very little time in each place, traveling at a "see some sights"/"work a checklist" pace (and not even all the majors), with little/no time to wonder small streets, linger over a coffee or aparativo, and be able to tap into the culture/vibe of the destination.

Edit to add: Very little time in each place except Toledo, for which you schedule a leisurely stay. Arriving in Madrid from the US I'm always landside in under an hour- usually well under. For a 6am arrival, I'd book the hotel for the night of the flight, and have a nap and shower while the city is still waking up.

We too we’re out of the airport within an hour of landing. Immediately after immigration you show your Travel Health QR code, get your luggage, and you’re on your way.

Most hotels will hold your luggage if you arrive early. Ours did in Madrid. At all the other hotels on our recent trip we were allowed to check in early if our room was ready. Only once was it not ready so we had a glass of wine until it was ready.

I will echo the comment that you don’t have much time in any one place especially since commute time will eat into you day.

While this is a relatively fast trip, I do not share the view that it is "too fast".

The one city where you do not have much time is Madrid, basically just one full day. If you are not "museum people", it is OK (and not everybody is a museum person, personally I seldom visit western art museums when I travel), but it will be tight if you intend to spend more than 2-3 hours in museums, total. I'll put it that way: if you value a thorough visit of the Prado (or Reina Sofia, or Thyssen Bornemisza) more highly than a visit to Toledo, then skip Toledo. Or just treat it as a day trip from Madrid, it will make logistics easier!

Otherwise, 2 full days in Seville, day trip to Cordoba, 1 full day in Granada, 3 in Barcelona: not very generous, but appropriate to me!

Writing off Madrid as only a stop for a few paintings in a couple of museums is a common viewpoint among users of these forums. There's a large, rich, modern-while-historic city that such an approach seems to completely dismiss.