We took the train and had a timed entry ticket to the Pena Palace. It was pretty "easy" in general. We took the train, walked to the Pena Palace (quite a hike), and arrived to chaos in the queue - despite timed entry. We were a bit early for our time (good chance to get a look at the outside of the palace), but what we saw were no clear groupings by time, no staff coordinating the lines, and quite a lot of folks (snaking down the road a bit) with varying entry times. IOW - unnecessarily disorganized. Regardless, we got through the line, toured the palace, and were on our way. To me, the tour of the palace was a big "meh" and I wouldn't do it again (nor have done it at all).
What I really liked was the Moorish castle. That was much more my style - open and easy to explore - and the one thing I would definitely recommend from visiting Sintra. So, your "bonus" option would be my "primary" focus.
Also, regarding the train ticket to Sintra, I'd recommend popping into the train station beforehand to get your ticket, rather than just waiting until the morning you are going. We waited, and the line for tickets was much longer due to so many folks also planning a day trip to Sintra (or elsewhere). Buy ahead when it is less busy and you can just head to the tracks in the morning.
Also, the weather we got in Sintra was a bit misty/rainy off and on. Not sure if that is normal or just when we were there, but plan on different weather between Lisbon and Sintra.