Congratulations on your progress! The feeling must be great when you release it into the world :)
1) Timeline is the best pick. After its introduction there are not so many reasons now to create your own custom event-based trigger scenes.
2) In terms of coding not much difference, but surely tile-based games have their own approach to cutscenes. I suggest to look into other games of similar genre to see what looks good and what doesn't.
3) You should have invisible "camera" sprite to which game would switch on trigger scene & follow that instead of player. You could use then timeline on your camera object to move it.