Do I need to attack a bunch of ships from that nation or is there a faster way to be able to attack their towns?

Do you capture any pirates and hunters in this version or are they automatically gotten rid of?

So the treasure fleet is never in a town when visiting it in this version? What about the silver train?

Can the treasure fleet info glitch out? I got a tip about it and waited around outside the target town but it never showed up.

This had me confused for a while too, but no, you don't! Just embark on land next to the city and walk right in. A dialog will pop up asking you to either leave town, enter town or attack the city, showing the number of soldiers defending it and the current size of your crew. Happy sacking!