What is your favorite way to organize and track levels?

Since I have began my new journey into game development I have often wondered how others are keeping track of their levels. I am planning arcade style games where the player progresses through levels and cannot go to a previous level. Imagine the game Balloons. If the player survives the round and pops all of the balloons they move to "round 2", difficulty is increased etc. The player simply sees the next round, but how is this configured/coded in the back ground?

For my games, I was thinking of simply keeping a global variable and if the player completes the round then the game will add one to the variable. This Global variable would drive the game to load the next level and certain objects being loaded for certain levels or difficulty being increased along with other level dependent things.

I'd use something like arrays/json. It depends a little on what I need to load. So yeah, global variable that increases by one and loads a different set of data from an array.

That's how I do too. I have a currentLevel variable which I increase when players finish the level then I restart the layout and lod the currentLevel from an array or JSON.

A good answer depends upon if you are you using multiple layouts? Like one layout per level? Or are all levels in one layout?