Berserky
Personally, I think it is not a very good idea to make an openworld in a side-scroll because you loose sufficient time to make your linear world more interesting.
I memorise an old game which is known as Crusaders of Might and Magic which was released on Playstation 1 and then on PC
The first game is what I really love and it was linear. The interesting fact is that in ps1 NPC'S take decisions through the game, showing that they are alive. In PC there was characters without showing their individual characteristics, they haven't done all (only give a quests) but the world was not linear and game is known as a trash game.
In my opinion, open world is a luxury if you are an indie developer, and if you will concentrate all your attention on open world as the main goal you will collapse