Tomar and Knights Templar areas

You might want to look at a private tour in Sintra. It’s on the side of a hill and the sights are spaced out. You can meander around the small town but it’s a bit of a haul to the sights you want see although there are tuk tuks and taxi’s to take you up the hill. The Well like the Palace is extremely popular and the lines long so people advise to be there when they open. We had a guide for the day and among other places, she took us to the Palace of Monserrate versus Peña Palace, stunning interior and beautiful gardens and not crowded.

For Tomar and the Knights Templar you should check this group out.

https://templarknights.eu/tours/

You will likely need to take a bus to Tomar. If you haven’t found it, the train website is cp.pt. I just tried to look at connections but it isn’t coming up this morning. I’m thinking the train connections will be much longer than the bus. Flix Bus and Gypsyy are the two I’ve used.

The Knights of Templar Convent is right above the town of Tomar on a hill. It is definitely worth your time. A private tour guide might work for you.
I like staying in the Rua dos Flores area of Porto. It is flat and easier to walk than the Ribeira area. I wouldn’t stay in Gaia since most of what you will want to see is in Porto. Especially if you aren’t interested in wine and Port.

Quinta de Regaleira is where you find the Initiation Well. Buy tickets ahead of time. It’s a fairly flat walk to the Quinta from the downtown area. Be aware Sintra has a lot of hills when choosing your accommodations.
For Lisbon, the Baixa area is flat. I think someone mentioned a tuk-tuk. They are great for a good overview of some of the city. And, they save climbing the hills.

In the Baixa area is a Roman site that was found when Millennium Bank wanted to dig a parking garage. They give free tours of the site in English. It’s easy to find. I think it’s on Rua Augusta. You can stop in and reserve a spot for their next tour - if that’s something that interests you.

We were in Tomar two days ago and I found the Tomar castle side very interesting. No admission cost, but lots of climbing up and down stairs along the walls. The attached convent, with admission $$, was less interesting to me.

We decided to stay in Sintra rather than Lisbon so we can enjoy meandering between sites without rushing.<<<<<<

I would really advise against that. There is SO much more to see in Lisbon. I was just in both places last week and Sintra is so jam packed with tourists that “meandering” is very difficult. Many would advise doing an overnight in Sintra, as the town becomes much more calm and enjoyable after the day-trippers leave. But if you only have three days, I’d stay in Lisbon. Whatever you decide to do, I’m sure you will enjoy your trip!