You don’t mention which tour company you are considering, but I highly recommend Lisbon Riders.
I took 2 tours with them this past March: 1) Sintra and Cascais and 2) Fatima, Nazare and Obidos.
https://lisbonriders.com/group-tours/sintra-cascais/
https://lisbonriders.com/group-tours/fatima-nazare-obidos/
The first tour, with sintra, was fantastic. Great guide and I enjoyed all 3 stops on the tour.
With the second tour, the guide was not great, which I’m sure impacted my feelings about the tour. I’m Catholic and I did not enjoy Fatima. I think you have to be pretty religious to appreciate it. Now seeing the pope and St. Peter’s in Rome, that was impressive for me. I did really enjoy Obidos and Nazare was nice.
So, I would go with tour # 1.
Some details from my trip report if you’re interested:
https://community.ricksteves.com/travel-forum/trip-reports/solo-in-lisbon-portugal-my-trip-report