Is this really railroading though? I feel like railroading is when the DM says “you want to find a barber instead of visiting the king and queen? Alright, on your way to the barbershop, the royal footmen see you and say “adventurer! Come with us! The king and queen are looking for you!”. Perhaps in a more strategic context, it would happen when you say “actually, I think the king and queen are bad and I want to join the other faction” so the DM has the other faction kill your parents, friends, and pets before an overly sympathetic royal agent finds you in the other faction’s dungeon and says “the king and queen are busting you out of prison! Let’s go speak with them!”

It’s not always bad, but afaik, it’s defined by a DM not letting players do what they say they want to do.

I feel like the campaign plan from OP is just how to get your players to help you write the campaign lol