From what I know there's no issues with any of the cheats. The only thing you have to be careful of, I think, is some of the building cheats, such as 'moveobjects on'. Not because it will cause issues with the game itself, but you could inadvertantly cause pathing issues for you sims, and then you'll spend a few hours scratching your head and wondering why your sim is constantly stamping their feet and waving at you.
MrsFlynn will be able to tell you more in depth about the pack files, but essentially a pack file contains objects, so if you purchase a set from the store, it will come as a pack file which opens in the launcher then you can install it. One thing you can do is if you create a sim, you can save the sim, then copy and past the pack file (containing that sim) elsewhere on your computer. That way you'll have a backup of all your sims.