Track rail

Questions about the prototype and how it is modeled. I'm planning to model in the 1930s era, but I'm a long way from there.

Do they now use welded rail? If so, when did that start? In the early days, I believe they bolted rails together with "fishplates". For that matter, how long are the rails? I recall reading 39' someplace. In the movies you see a crew replacing rails but they never show bolting the rails together.

In the model, is it necessary to notch flex track to give the clickety clack? Or do you get that from the sound card? Or can you even hear that in a model? I remember a song with lyrics that mentioned the clickety-clack of the railroad track taking you back ....