Portugal itinerary help, please

I would rent a car when leaning Lisbon and drop it off when arriving in Porto.
If you want another car in Spain take a train or hire a driver to get to a car pick up location north of Porto in Granada.
This is to save from paying high drop off fees in a different country.
I recommend:
Lisbon (stay)with day trip to Sintra
Evora - stay in Evora, historic town
Obidos-spend a few hours but do not stay there. It is sadly one of places that today exists solely for tourism.
Alcobaça- the basilica, burial site of Portugal’s royalty
Nazare- have a seafood lunch by the beach then move on.
Coimbra- university town, a top site in Portugal, stay in Coimbra.
Aviero- stop for lunch
Guimares( stay) Portugal’s first capital, interesting place to explore
Porto- stay-drop car upon arrival.
Instead of traveling to Sakamanca( or in addition to) From Porto take a train or hire a drivers to nearest car rental location in Spain. Use AutoEurope to find that location.
Drive through the beautiful Rias Baixas area of Galicia,Spain, then head to Santiago de Compostela where pilgrims have arrived on foot( and now also on bikes) after their journeys across Spain on the Camino since the days of King Ferdinand and Queen Isabella.
Next Leon is a wonderful stop.

This is sooo helpful. Thank you very much!

I'm not aware of buses with lie-flat seats and would expect an overnight bus to be a totally miserable experience. I took them a few times in the US as a college kid. Never again. I will happily string together two days of 8+ hour bus rides with a night in a hotel bed in the middle to avoid an overnight bus trip.

I want to correct one of the things suggested above. There is no train from Cascais to Obidos. The only train in Cascais goes to Cais do Sodré in Lisbon with a number of stops on the way.

I also would not suggest Obidos for one of your major stays. It’s ok for a day trip but is small and crowded and would be even more so during a festival.

Salamanca is worth your time and effort. But, there are many small historic towns between Porto and Lisbon. Coimbra, Tomar, Alcobaça and Batalha come to mind. A car would be helpful to see these areas. The good news is that driving in the central part of Portugal is easy.

Karen, I deleted my answer because I used the website: https://www.cp.pt/passageiros/en/train-times/Train-time-results#! for the first time and failed to click on the details (+) sign that showed there was no direct train between Cascais and Obidos. According to Expedia, you could rent a car in Sintra and drop if off in Obidos: https://www.expedia.com/carsearch?date1=11%2F2%2F2021&date2=11%2F3%2F2021&dpln=4694&drid1=4390&loc2=Obidos%2C%20Leiria%20District%2C%20Portugal&locn=Sintra%2C%20Lisbon%20District%2C%20Portugal&time1=1030AM&time2=1030AM.

I'm going next week to:
Lisbon (three days/two nights), Cacais (an hour or two), Sintra (two nights), Obidos (one night), Nazare (two hours or so), Coimbra (two nights), Evora (two nights).

Plan to stop at Alcobaca Monastery and Batalha Monastery either driving to or from Coimbra.
Saving Porto and the North for another trip.

What I do is make lists of "Things To Do in Sintra" (for each city) that I take from several sources, including Rick's guide.
We don't do everything on the list, but it really helps to figure out what to see next. I've got Lisbon organized by neighborhood.

I'd be happy to post the lists, but don't think I can add a pdf. Email me glen@pos.org if you want a pdf of it.

Evora, do on a day trip from Lisbon.
Porto, stay in amazing B&B, The InPatio Guesthouse, also take the train up the Douro River for a couple of days, or a river cruise.