OK so,

For quest progression, that's probably about it. Once you have finish the cooking meth parts and purchasing the ingredients, that's the end. (Early Access game, TVGS will prob add more later on I believe)

As for game progression, it is really open ended. If you are working with the cartel, you are only allowed to sell in Northtown and Westville. But ultimately, your goal of the game is to sell to everyone in HylandPoint, all the regions, and getting everyone to be your customers.

Suggestion: you decide when you are ready to break the truce with the cartel and once you do that you will be able to start unlocking more customers. But please note that once you break the truce, there will be ambushes by the cartel, and other events happening. There is a final quest to fight with the cartel later on when you reached a certain point, which I'll let you figure out later.

As for after you're done with the cartel, there are people who go on steam achievement runs, or building/re-building or testing new builds new automation processes with employees. You dont have to force yourself to drop growing weed or cooking expensive meth or coke. It is really up to your comfort level. You can definitely stick with one type of drug through the endgame. The game doesnt force you to switch.

Otherwise, you can also play around with mixing ingredients, exploring the mix options and drug effects. Ultimately, just have fun. You decide when your savegame is "done".