Wondering if we should plan a day/night in Viana do Castelo before or after a few nights in Porto? Would appreciate thoughts on this and lodging recommendations.
When in the year? Outside of summer season I don't think it's worth it, as it's mostly famous as a beach resort these days - although it is very attractive architecturally speaking.
I would say that overall, Guimarães or Braga make better overnight destinations from Porto, there's more to see and they're easier to get to. As for Before/After... It all depends on where you're going to after Porto and where you're coming from before Porto.