We did Porto and Lisbon in 2019, and it was one of our favorite. If I recall correctly, we took a day trip to Sintra and Cascais from Lisbon.
Mine is not much use for planning, and I realize now some notes would have been helpful, but it includes some pictures of both places, and maybe ideas for bring things back.
@mariacarmen 's thread is great! I don’t know if I have seen the one from @Maribel , but I have also linked another trip planning thread, in case you haven’t seen it.