You know I'm just going to go back to the original question. How much railroading?

Railroading as the removal of Player Agency (the standard definition): None, decide how much player agency is in the game and stick to that. Now you can have a game that is wide open and full of decision points about how the party changes the world or you can have a game that is about small group tactics and listening to a story. Both are fine, but don't present the first and run the second.

Railroading as running a Railroad, a Linear Adventure (seen it in a couple of places): Varies, it just relates back to the campaign structure. As above there are many options all of which are fine. It is just a matter of finding one everyone around the table will enjoy. And as above, present in honestly, if people don't like your play style labeling it as something else is not going to help.

Railroading as the GM providing guidance (as Darth Ultron uses it on occasion): Whenever the players need it. So probably in a hunk at the beginning of the game and then other bits and pieces when they get lost. Or you can give them a moment to find themselves, that works in our games because the players (and hence the PCs) rarely just wait for something to happen.