The basic answer is that you have to set every sim individually in CAS via manage worlds. It is time consuming, but I do that with my own base save and only start new games with my base save. I also tweek setting in my MCCC mod to achieve desired relationships allowed in-game. Like I said it is a tedious process, but doable. I also delete all sims which do not fit my desired gameplay and only import my own sims to help with that. It is a long process, but can easily achieve whatever style of gameplay a person wants.
As for the SDX drops, there isn't a way to delete them once in-game. You could search for mods to hide the content you don't want to see. I have done that with all the Star Wars content and some other content I will not use. Searching on the internet, I am sure you might find mods that are helpful if you play on a computer.
