We did this tour last May, but had already done a similar itinerary, so we only chose to do our favorites a second time - those were La Sagrada Familia and The Alhambra. We like the Picasso Museum and Parc Guell monuments area in Barcelona, but I understand that the latter has gotten much more crowded. I was fascinated by the concept of a designed community but if I had to chose a “wow”, I would say Palace of Catalan Music and would definitely try for a concert. I think most everything you want to see in Barcelona needs reservations just because of the crowds and making sure you don’t waste time. Are you adding any extra days in Barcelona?
In Madrid, the Royal Palace and the Prado were my favorites the first time and I think both need pre-booked times. The Alhambra in Granada absolutely needs reservations and should be done as soon as possible. You’ll need to pick a time for the Nassrid Palace, which is inside the complex. We went first thing in the a.m. before the crowds got started. We didn’t book anything in Ronda, but enjoyed touring the bull ring & museum. The Alcazar in Seville is a must. Our one mistake was not booking the Cathedral in Seville. It ended up selling out the weekend we were there and there was no walk-up option.
Sometimes the guide will offer an optional activity. Our guide organized a dinner in Granada over-looking The Alhambra and we watched as the sun set and the lights came on. The was a real “wow” so if that isn’t offered, it would be worth arranging yourself and the guide can help you with it.
I’m happy to answer any other questions about this.