Itinerary HELP! 12 days in Portugal - flying in and out of Lisbon

Often, when I don't know where to start itinerary planning, I look at group tours to the destination. That framework is always well thought out and can serve as a good launch point for me. (Making changes per my own priorities, and knowing that I'll be managing transportation on my own.)

Here's the RS 12 day Portugal. Maybe it could help you get un-stuck. https://www.ricksteves.com/tours/spain-portugal/portugal

I don't know Portugal so I can't tell you what to do, but I can hopefully offer some suggestions for tackling this stuck feeling.
1) Have you checked on the car yet? Prices are reportedly way up, so I would nail down the non-car part.
2) I don't like to split my stays, so if you can determine where to go first where you can end up in Lisbon last, that will help. My husband is the driver and he can drive up to two hours after an overnight flight--we don't do more than that on arrival.
3) Do you have a guidebook? I find using that for transport basics helps me avoid getting bogged down online, but I would first determine which places are reachable with transit, which are better with a car, then group the places together. It will also have sample itineraries and good driving routes. You don't have to reinvent the wheel.

Add what month so Portugal experts can advise you--for example, I would avoid August in the Algarve, but that would be a great time for the north.

Sorry, you don’t have time to cover the Algarve, Lisbon, Porto and areas in between. When is the trip? Does your 12 days include arrival and departure days?

You could spend 5 days in Lisbon plus a day trip to Cascais or Sintra then hire a car and drive to Porto, visiting Tomar, Alcobaca, Batalha etc en route before spending 3 nights there. If your flights aren’t yet booked, it would save time if you flew back from Porto.

Our trip is the last two weeks of June. Flights are booked. 12 days are on the ground not including travel (day 1 we arrive at 8am). I thought of flying out of Porto but that adds a stop for us, so it added more travel time and not worth it. Flying in and out of Lisbon we only have one stop at Lisbon ---> JFK --> AUS

What month are you traveling (weather can come into play)? What are your interests? How fast do you like to travel?

I'm planning my 3rd trip to Portugal and have just touched the surface.

With 12 days, for me, I wouldn't do both Porto and Algarve, but pick one direction or the other. And to add to your list, there's also North of Porto (Guimaraes and Braga) and the Douro valley.

The Silver Coast is rather nice if you like small towns and beaches.

Another resource for planning is Julie Dawn Fox. I find that she is good at providing information on some of the towns that aren't always covered in the guidebooks.

Edit to add: We flew in and out of Lisbon. When we flew in, we took the train to Porto to start there. Figured that the day was already lost and just napped on the train. Once leaving Porto, we picked up our car and spent time on the Silver Coast before leaving the car prior to Lisbon.

We are going to Portugal for 3 weeks in June. St Joao festival in Porto June 23, rooms are limited at this time. I suspect will be crowded this year, but looks like a good time. Our schedule did not meet up with this festival. As mentioned previously car rentals are expensive and gas will be too. The intercity or regional trains goes to/from Lisbon- Sintra, Lisbon- Cascais, Lisbon-Evora, Lisbon-Faro (can get off in Tunes to connect bus or regional train to other areas of Algarve), Lisbon- Coimbra- Porto. Train strikes are happening this month on March 11 and 18 between 5-9am, but are scheduled so you know before hand. I suspect there will be train strikes all spring and summer since per hotel availability and price increases it looks to be prepandemic levels of tourists.

https://www.cp.pt/passageiros/pt

I gave up on train routes after my sister in law rented a van for our trip, its quite expensive, but I will not have to listen to my brother in law complain about needing to be at the train station at a particular time, just about the distance, gas prices and parking. (I'm going to need a lot of wine)

My itinerary:
Lisbon 3 nights- I booked a Cascais/ Sintra tour with We Hate Tourism Tours and plan National tile museum, some walking (pick up rental van on way out of city)
Lagos 5 nights - I booked a sailing trip with Bom dia en Bahia and plan do some hiking/walking and beach
Evora 1 night- I want to see the Chapel of Bones,eat Alentejo black pigs and drink Alentejo red wine.
Porto 3 nights- I booked a tour to Douro Valley by van via Oporto Road trips for more wine and a short cruise on Douro River
Viseu 3 nights (visit family and a wedding)
Praia de Veira 4 nights (visit family)
Lisbon 1 night (drop off rental car and fly home next morning)

My Mother in law was from Mangualde near Viseu and my Father in law was from Carvide in Leira,my brother in law is from Gouveia, my husband is from France. My first time in Portugal was in 2011 for an overnight layover in Lisbon and my second time was on pilgrimage to Fatima in 2019 by myself with local tour group. My husband and I never had vacation time in July and that was the only time his familiy would visit Portugal until now and only because of the wedding.

Happy Planning!