As for Cascais…
The Castle thing looks quiet and nowty but there is a nice bar within it, nice place to sit with a cold drink.
If you are on the beach and the locals all start packing away and leaving , that usually means they aer about to release a bull on to the beach.
Continue thru Cascais to the Atlantic coast (walakable), theres a lighthouse converted to a bar and the beach runs for miles with pretty wild waves, lots of surfers, goes all the way to Sintra (i think). Seom pretty good mtbing just off theat coastal stretch.
I lived in Cacais for a year or so, but was a while ago so memory a little fuzzy,