Hi! I just wanted to share how I solved the choppy game problem of mine, in the hope that this also works for you. I was one of the unfortunates who suffered from a choppy game after I installed LN and FL. Choppy means the action pauses for like one to two seconds before it executes, it was a nightmare! To solve this I've tried to move my video files to another drive, delete files in my game drive to give more space, etc - nothing worked.
By coincidence, one of the Sims in the choppy household had to travel. So off he went with his grand-daughter to France. I noticed at once that the game speed was normal, movement was fluid in the France world (outside SV). I figured that it wasn't my computer nor the EP that was causing the choppiness, it was TOWN DECAY (I'm not certain whether I am using the term correctly), but I have noticed that my Sunset Valley was getting over-populated (being the oldest town I played), the original SV populace were elders . I have town progression and aging off (maybe that's the culprit, I don't know).
I figured it was SV that was causing the chopiness. So what I did was to copy each family I created into the family bin (some with their own houses) and some just the families. (It can be a chore if you have many families you want to save). Then I deleted the old/decayed SV, I ended that world. Then I created a new SV, and put my Sim families there. Now I am happy to report that the speed of my game has returned to normal. ! Hope this post helps some!