Your game probably will be a little slower while it regenerates things. At least, that's always what I have assumed, as when I delete mine, I sometimes suffer from "white box syndrome" in which objects appear as white squares for a brief moment before rendering, until everything is loaded, and after that I don't have trouble.
Until then next time it's cache deletion day. Some people don't delete them, some do it rarely, but I do mine after every couple of play sessions. It's just one of those "voodoo" things I do to try and keep my game running nicely.
Like @Mikezumi , I also only install a few things at a time, and have a subfolder named _Test_ in my mods folder, so that I know which are the latest testing files, so if issues occur, I know immediately where to go to find the culprit.
From early on, it was apparently determined that some game slowdown ( besides corrupt CC etc ) could be attributed to the sheer amount of package files that the game had to read, which is why merging seems to help I suppose. It was also mentioned that each merged packed be recommended not to exceed 400mb in size, with the "optimum" speculated to be at about 200mb.
Someone more technical could probably determine if that were a hundred percent true, but those are rules I've always kept to, and I have rarely encountered game issues. When I have, it has been either an EA problem, or simply a mod I stupidly forgot to update.
I also keep Save Cleaner, and package Viewer on hand, the latter which is particularly helpful for locating a hair, or object that you might actually want to remove from a merged package. ( This happens to me a lot lol - I just go off things and don't want them anymore )
